A couple of packs of dry snack foods -- some cookies and some chex mix, usually, plus water and a few small soft drink bottles (which we use to refill the drinks we buy at meal stops.) We're not picnicers by nature.
I agree with pp about part of the fun of roadtrips is stopping and eating along the way.
I do pack snacks such as cheese crackers, jerky, sunflower seeds, choc. raisans, fruit snacks, goldfish crackers, small cookies, etc. We also always keep a case of bottled water and a case of juicy juice under the seat. That saves a little $ than buying drinks for the kids (5 of them) at a fast food place.
I too, pack wayyyyyy to much food. Dh gets mad at me cause I pack enough to last us a week
If you want to stop somewhere that is kinda on the healthier eating side, subway is good. Some have drive up windows. My kids also love the parfaits at McD.
We have decided that we will stop for meals, cause we need to stretch, and just pack some fruit and drinks. We are getting up at 4am and jumping in the truck. Hopefully we will reach the Pacific Ocean before the last ferry leaves for Victoria.