The six kids looked strange as they headed east on the highway while the rest of the crowd went in the opposite direction. They all felt uneasy, and now realized why Ethan had wanted to stick to the woods. Yet, they were stuck on the road until they could pass the cut out, the high walls of rock that enclosed them would be impossible to climb.
“Up ahead…” Carter announced, pointing up the road. Ethan had seen it too. An un-mounted convoy of two-dozen or so U.S. infantry was heading toward them.
“Ok, Jason, hide the SKS, let’s rest here until they pass.” Ethan said as he took off his pack and set it down on the side of the road. Jason un-slung the rifle from his shoulder and laid it in the tall grass and Allison smoothed the surrounding leaves over it with her foot.
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*The six kids looked strange*THE - Starting a story with the begs for the word or words following it to be extremely descriptive or specific.
SIX - ok.
KIDS - What kind of kids? Right now six is all I have to go on. I don't know anything about them including what I'd consider to be an important first impression - their age.
LOOKED - Looked as in they are doing the looking, or I'm looking at them?
STRANGE - How? The whole sentence has been building to this word and strange is too general.
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KIDS - Even after finishing the 13 I don't know their ages. I'm going to assume they're teenagers since one's carrying a gun, but teenagers is a boring description. I'd rather see their situation through an adjective used to describe them. In order to do that, I must remove the word "Six".
Now you've got three words to play with.
Can you call them "armed" Probably not in today's world. How about "Camouflaged"?
They may not be camo'd in your mind, but they're strange and that should stand for something visual beyond merely the direction they're walking.
Perhaps they are all dressed in leather overcoats like the people in the Matrix. The agents wore suits and sunglasses, the good guys wore tight black leather and sunglasses. They visually stood out from everyone else.
Camouflaged could make them military though and since the U.S. infantry is coming and they need to hide their gun, that won't work.
You could use a foreshadowing placeholder instead. "displaced". This is assuming they are which I'll learn past the 13. You however, know now.
THE DISPLACED
Not the greatest visual, but it's moody. Tells me someone isn't where they belong and probably didn't like the idea. Two words in and we have conflict.
"youths?" Too My Cousin Vinnyish. "teens" maybe, "friends" maybe, but are they? If you call them friends I'll expect them to get along and if they have infighting, why'd you call them friends? "high schoolers" it's two words, but it fits with displaced and gives me their age and unifies them to some degree. They're on a trek together, they're not at school, things aren't normal. Let's see if the extra word is worth it.
THE DISPLACED HIGH SCHOOLERS
LOOKED - "appeared" as it's not how the reader views them, right? But how they'll relate to others in the story.
THE DISPLACED HIGH SCHOOLERS APPEARED
Here comes the money word. How do they appear? This 13 is giving me a "Red Dawn" feeling. I'm going to go with that.
Are they tired? Frazzled? Nervous? Edgy? Later on you say uneasy.
THE DISPLACED HIGH SCHOOLERS APPEARED UNEASY AS THEY HEADED EAST ON THE - what highway? "The" is not a good adjective to describe a highway unless it doesn't matter and I feel like it does. How far in the future after a calamity are we? Was there one? Was it physical? Is the highway endless and describes how they feel about it and life? Let's remove the word the and call it abandoned for now as this removes cars from the equation.
THE DISPLACED HIGH SCHOOLERS APPEARED UNEASY AS THEY TRAVELED EAST ON AN ABANDONED HIGHWAY.
*The rest of the crowd went in the opposite direction*
You use "the" two more times. Four times in one sentence.
THE REST OF THE CROWD - this tells me there is one crowd and the kids are a part of it. Yet, they're traveling a different direction. Did they all start in the same place? It seems to me the kids met the crowd along the way when they didn't take the woods. Also, let's populate your world more with the addition of only one letter. "crowds".
Now let's describe them. What do they look like. How are they NOT strange. To answer that we must know their motivation. Going with the Red Dawn theme, and the kids being displaced, and being on foot on a highway, I'm going to make them downtrodden.
CROWDS OF PEOPLE SHUFFLED PAST THEM IN WAVES.
The word shuffled indicates aimlessness, and weakness. Crowds and waves indicate a large scale exodus. The kids walking past them (opposite direction) indicates strength in the small group.
*They all felt uneasy, and now realized why Ethan had wanted to stick to the woods.*
I know you've said Ethan isn't the leader, and you're writing in OMNI, but I'd recommend strongly against it. OMNI is as out as teen vampire stories are in. It's distant, and hard to identify with and attach to any characters. i.e. care. Would you rather read about "the resistance" or John Connor?
I'm going to proceed 3rd person, so you can officially tell me to stuff it from here on. (if you haven't already)
We've established their uneasiness in the first sentence and saved a few words. They've been walking past waves of people, so a sudden realization is out. Ethan wanted to take the woods but was overruled. Where does that leave us? Conflict.
You can switch to dialog, an argument or an I told you so, or go in Ethan's head.
*Yet, they were stuck on the road until they could pass the cut out, the high walls of rock that enclosed them would be impossible to climb.*
-Ethan felt trapped...
-Ethan felt claustrophobic...
But these are both telling.
Try: "Ethan glanced back and forth, trapped by vertical rock on two sides and hordes of refugees from the front."
It's easier to identify with one twitchy person than tell how a group felt en masse. Plus we've added another description to the crowd(s) of people.
*“Up ahead…” Carter announced, pointing up the road. Ethan had seen it too.*
Is Carter a first or last name? If last, use both names until it's established how they talk to each other or how you as author plan to use the name. (Same should go for Ethan)
Tense shift. - PointING - Ethan HAD seen it.
Announcing is ok, but if this is Ethan's story, he should say it. If you keep OMNI then don't mention Ethan seeing it too. You're only strengthening my innate desire to latch on to someone by mentioning him a second time and picking him out of the group. Also, up the road can be omitted. You've established they're on a road, and surrounded by sheer walls.
*An un-mounted convoy of two-dozen or so U.S. infantry was heading toward them.*
Unmounted as in horses? If so, they are cavalry, not infantry. If not, why mention they are unmounted? Also, right now this is merely information. A group of teenagers is walking against the flow. Up ahead are military. But since there are words like Displaced, Uneasy, and Trapped the mood is set for the opposition to be negative. Plus, Carter simply said "up ahead" instead of something like "we're saved".
WAS HEADING - how about marched? Military personnel march. It's with purpose. It's imposing. It's active. It saves a word.
Now lets go back to Ethan's woods.
Try: "Up ahead," Carter announced. "Military," Ethan replied. "I told you we should have taken the woods."
This says all kinds of things.
Military = Bad. Ethan = overruled or not in charge. Plus it removed a whole sentence of telling and makes it active.
*“Ok, Jason, hide the SKS, let’s rest here until they pass.” Ethan said as he took off his pack and set it down on the side of the road.*
Now you have Ethan giving orders and doing an action. This story is totally about him. Set your subconscious free!

SKS. I had to google this to find out what it was. Use RIFLE instead. This seems to be a rare case of the generic being better, but only because it's such a specific gun's name. (I think)
If the military is bad, let's have the group fear them somehow, or at least prepare to fear. Instead... they rest. It's building, then it crashes. If you're starting the story at the moment of incitement, this sounds perfect. Or at least it's setting us up for a tense scene in which we may learn more about the group and the world.
Try: "What do we do?" "Play it cool," "Let me do the talking." "Retreat." "Let's take the woods. It's too late for that." "Hide the rifle."
*Jason un-slung the rifle from his shoulder and laid it in the tall grass and Allison smoothed the surrounding leaves over it with her foot.*
RIFLE FROM HIS SHOULDER - this is saying that up until now, their walk has been casual. Or at least they aren't in immediate danger. It's mood and it's spot on, but to up the ante, have him holding it, ready to use.
JASON PLACED THE RIFLE IN THE
The word placed will change depending on the sentence leading up to it. If someone yells at him to ditch the rifle, he'll probably throw it, not place it.
TALL GRASS - needs more description. Is this a Mad Max world? Let's make it so by calling the grass "brown" or "dead" or "dry"
JASON PLACED THE RIFLE IN THE TRAMPLED BROWN GRASS
Remember there's been crowds of people walking this way.
THE SURROUNDING LEAVES
Tall grass and surrounding leaves doesn't jive. It works better with trampled grass, but to make it more active and set up a possible tense scene later on have Allison sit either on or in front of the gun. This way if the soldiers come along and "want" something from the only girl mentioned so far, there's the gun hiding behind her. If not, then their rest is forced, not casual.
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Ok, that's it from me.
Hopefully this wasn't too obnoxious.
Axe