I just did a 4 day car trip and what I packed was:
Box of Raisin bran, plastic bowls and spoons, a couple of quarts of rice milk. If you get the boxed kind, it can stay at room temp for a few days until you are ready to use it. Put it in the chest 6 hrs before use. We would stop at a rest stop and have a snack. We tend to get constipated on road trips with all that sitting. This cereal helps. Also, pack APPLE juice to help with constipation as well... but be careful not to let them have TOO much or you get the opposite effect!
I made homemade breakfast/lunch sandwiches by cubing up some ham (from a whole ham- its the best- not lunchmeat.)
I took a metal ring i use for making hamburger patties, sprayed it with oil, and layed it in a greased fry pan. (you don't have to use a ring) I pour in a layer of scrambled egg and sprinkle in the ham chunks. When one side is done I lift the ring and turn the egg over, slap on a piece of american cheese, and then put it on a split crossoint (I used mini crossoints from costco). Wrap each sandwich separately in foil, and fill up a gallon ziploc bag with them. They can store in the ice chest. When kids are hungry, there are 2 ways to warm them up, one, you just put it (still in foil) under your armpit for 5 minutes. Or two, open up the foil, exposing the top of sandwich , still on the foil, put in on your dash board. The sun will heat it in 3-4 minutes. These are the bomb. Some sandwiches get nasty when they sit already made, but these can last days and still taste ok. Plus all the ingredients in the sandwiches are "stuck" together, meaning less mess in the car. Don't forget to pack baby wipes for the hands.
Cheese: I have tried taking cut cheese for my apples in a ziploc and I always end up throwing it out. it just doesn't store well and gets a nasty taste and texture. Iv'e tried bananas too and on both trips they always get thrown out. They get too brown too quick from being warm. no one eats them.
I like to cut open a FUJI apple into 4 slices down from the top, core it, and then "stick it back together the way it was". Wrap each apple tight in foil. put apples in a ziploc.
We also took tostitos tortilla chips and a small glass jar of store bought guacamole dip.