You literally have ALL summer..
Don't worry about those little shits liking the food, learn how to make it cheaply and tasty.
I used to do the same at a summer school type of thing. I'll share some easy things:
>plan every meal like this: starch, veggies, meat and sauce.
1) Starches:
-Oven roasted potatoes can be made in 1000 ways. Different cuts, spice blends etc. Just cut into shape, oil + spice it up and pop it in the oven
-rice is easy as fuck to make
-Pasta, buttered/oliveoiled on the side or with a meat + veggie sauce boom easy dish for the day
2) Veggies:
-pick shit you would see at a sunday dinner, the classic stuff that most people will like. Top of my head: carrots, onions, peas, peppers, tomatoes cut in 2 with olive oil + basil/oregano
-simple salads with fresh stuff + bacon/cheese.
-Shit like broccoli or cauliflower can be made in a cheese sauce, eliminating the need for extra sauce.
3)Meat
This is all about budget control. If you have time then this can be done cheaply.. but tasty.
-Beef, dont bother unless it's stewed or slowcooked, usually expensive due to hipster making shitty cuts more costly nowadays
-Chicken
Butcher whole chickens, cook different parts on different days as you wish, cheap as fuck. (aka wing days, breasts couple of days, legs couple of day)
-Pork: bacon, ribs, pulled in a taco etc. all good shit. Just dont make something with whole lean pork since it WILL dry out. Same as beef just stew or slowcook for best results.
-Fish, expensive as fuuuuuuuuck if you pick things kids will actually eat, even then half of them wont even bother. If you do this then then just go with fucking fish dicks
-Other meat will usually be a bit expensive or will scare off the kids if they don't know it.
4)Sauce:
Easy, fucking make either roux-based stuff, cream stuff you just reduce or shit out of packets. No use making complicated fine dinish stuff here.
Most commercial shit available tastes well enough.