I know how you feel. :) I have a few ideas... I hope some of them will help.
First, it sounds like staying at home is your best bet now... with 2 little ones who need care all day and one who needs after school care!
You and your husband are going to have to make some changes. Figure out what you can't live without (the car!) and what you can either get rid of (expensive cable) or scale back (just get rid of movie channels). Surely, there are other things you could think of, too.
For inexpensive meals, try those Taste of Home magazines or cookbooks-- they have a section that shows how you can feed a family an entire meal (and dessert!) for just a few dollars. I used those a lot when my kids were younger and we were in the same situation as you are. Also, be sure to make enough food so that you can pack your husband's lunch for the next day from the leftovers.
Find someone to carpool with so you don't have to drive to school everyday-- you might be saving someone else's life, too!
How old are the kids? For the school-age one, maybe he(she) could help you gather unused clothes or toys or unwanted gifts and you could list them on eBay? Nothing to sell? Maybe hold a swap with your friends or neighbors to get clothes or toys that the kids need. Take advantage of the fact that the little ones don't know what they're wearing and don't care! Don't worry that they don't have lots of clothes-- don't need 'em!
Make a budget and stick to it. Find out a way to pay your highest interest cards first while just sending in the minimum to the rest (I know, stay with me!) Once your high interest card is paid off send the amount you were sending to that card, say $200, to the card with the next highest interest rate or amount. Plan this out on paper or on your computer. I did a spreadsheet on Excel and it would calculate for me how much I still owed and keep a running total every month.
When my oldest, now 12, was 3, I used to grocery shop on $50/week! You'll have to shop the sales and use coupons, but it will pay off. (I also used to notice that they marked down the chicken and other meats on the day before the expiration date. Note those and go back when the prices are lower... I'm sure you'll find your own crazy, little way of saving money, too.
As for the kids, just find creative ways for them to play. If you're working on something outside, give them a bucket of water and a paintbrush and let them "Paint" the walls-- mine loved this! They'll never know that they were broke-- they'll just know Mommy always had fun things to do and was home with them.
I think once you sit down and just come up with a plan, you'll feel more in control of the situation and not like you're floating down a river with no way to get out. Hang in there. Good luck!