We just got back and took a huge rubbermaid container full of snacks-granola bars, crackers and cheese, fruit snacks/roll ups, indvidual pudding, individual fruit cups, individual packages of Dad's oatmeal cookies, oreo cookis, little packages of ritz crackers and cheese, oatmeal bars etc. We also bought drink in box juice and kept it in a cooler.
We also bought a little compact oven that plugs into our lighter and it fit great on the dash--we could cook a mini pizza in 1/2 hour so it was continuously cooking---it also was great for heating up pre-cooked items.
We bought a cheap toaster at Wal-Mart(cost $8) and when we crossed the border we picked up bread and cereal to eat breakfasts, had packed peanut butter, honey, etc. When we were done with our holiday we just left the toaster. Try to find hotel's with complimentary breakfasts, eat big breakfast then go, with snacks in vehicle you should be able to get away with only buying one meal a day on the way down!
Also took instant oatmeal and Kraft dinner Ready Mac in case any rooms had a microwave--------all this saved a ton of money on food.