While I agree about the planning, I think it depends on what the root cause of the junk food fest is.
If it's because you all are stressed and it's your reward
, then you need to find a new reward your family can agree on - taking half the money and putting it towards toys or a vacation fund; going out for walks and bike rides or to local festivals as fun/reward; having a family movie night or picnic or "t.v. dinner night" (dinner in front of the tv) instead; ice cream from the freezer.
If it's because of the speed/convenience
then meal planning is the way to go. If you have a BBQ, use it - it's fast and easy to throw something on the grill. Develop a menu of easy stuff. Do prep ahead. Or throw some of the money at convenience products like prewashed/chopped veggies. Do not get sucked into the idea that the choice is:
Fast food vs.
lovingly prepared all-locally-source-organic-5-course-dinners.
Soup, even from a can (although pick your can
) and grilled cheese on whole-grain bread is still going to be better for you than the meals you mentioned. Or make-your-own sandwiches. DO NOT GET PERFECTIONISTIC.
Every time you stay away from the fast food, it's a victory. The rest will come.
If it's the taste
then you have a few options.
First you can ease your family down by using some of the (gross but remember you are on a PATH, not PERFECT) stuff in the store designed to taste like fast food.
For pizza, for example, you can go from Pizza Hut to a premium frozen pizza to a deli-in-store made pizza to store-made pizza crust/dough to your own, over a year. For burgers and fries you can go from frozen patties and a whack of condiments and frozen french fries gradually to turkey burgers and roast potatoes. Take your time.
I agree about stocking the car with some snacks too.