Here is an idea that I admit I have not tried myself, but I have read of others doing similar strategies and finding it to work well.
First, make a menu for the week, include breakfasts, lunches and dinners.
For example, plan on inexpensive breakfast burritos for the week day mornings..... and write down everything needed to make enough for everyone in the family for the week.
Plan the lunches for every day of the week. PB&J, perhaps? Tuna? Bologna sandwiches? Write down every ingredient for each lunch needed during the week.
Finally, plan the dinner menu for the week. Again, write down every ingredient you will need, down to the Parmesan cheese for spaghetti.
When you do your shopping, do it alone if possible to avoid impulse/bribery buying that kids have a tendency to encourage us to do.
Now, the fun part. Sometimes just having a " menu plan" and necessary ingredients sitting in your kitchen are not enough to stop you from impulsively ordering food, or running out to pick up fast food somewhere. If you are too tired and frazzled to feel like cooking....you probably won't. So the more meals you can have made and sitting in the freezer ahead of time, the better. Taking out a casserole and heating it up is not as bad as having to chop, cook, bake, and finally eat. With some thought, cookbook browsing and creativity, you can make meals that can for the most part be prepared ahead of time and ready to go.
So after the shopping..... use some of Saturdays and/or Sundays to Cook! Make the breakfast burritos for the week ahead, and freeze them. Come a frazzled Monday morning, you will be less tempted to herd the kids into the car and stop for a quick breakfast "on the way" to school. Just grab the burritos out of the freezer, heat and eat--even "on the way" to school.
Then make as many of the lunches as possible for the week also. Depending on what is on the menu, you can make ahead the snacks, drinks, cut up veggies and fruits and have them ready to go for each day of the week. Less chance of pulling out the wallet for cafeteria food if lunches are set and ready to go.
Same routine with the week's dinner menus. Plan and cook and freeze as much as you can. Have lettuce washed and separated for easy salad making. Freeze spaghetti sauce. Make the casseroles and freeze them. If you have desserts, plan and prepare as much of those as well.
The main thing is to have meals ready-to -go as much as possible for each day of the week. If you do this on the weekends, you should find yourself avoiding spur-of-the moment pizza ordering (adding tips..expensive impulse move!), picking up fast food, and eeeek....going to a restaurant when you really can't afford to, just because you are too tired to grocery shop and cook. And if doing this for each day of the week sounds too daunting...try for it for two or three days of the week. Or just do it for breakfasts or for dinners. Just try to incorporate some cooked ahead meals into your week to give yourself a break and your wallet!
It does take some time, planning and energy cooking on the weekends, but your weekly budget so get some relief, and you may even lose some extra calories skipping on the fast food dinners and lunches!
check out: Black Bean Casserole Recipe to make ahead and freeze.