Hello to the Housewife! I, too, am a stay-at-home mom. I have been fortunate enough to find a church that has a "Mother's Day Out" program. For a very small fee, they will watch kids for about 3 hours, 2 days a week. I am planning to take advantage of this service.
Also, I have to do a lot of my writing after the family goes to sleep. I know that these solutions aren't very satisfactory, but I figure they're the best I've got, so I'll try to take full advantage of them. Even if I only get an hour a day, at least it's something.
Another idea you could try - find out if there are other moms with kids the same age as yours who might want to start up a "playgroup" type of arrangement. You could take turns watching the children, giving one mom each turn a chance to be by herself.
Good luck, I know it's not easy! If you come up with other good ideas, please share them. I myself am not a very good housekeeper, but I do try. I'm hoping that by giving myself a 'regular writing time' that I can manage to be more focused during housework time.
I also ran across a Writing Mom's website when I was doing a random surf on the 'net. Unfortunately I don't remember the address. I bet if you can find it, there will be a lot of good ideas and some support for the unique challenges of writing mothers.