My daughter and I are heading out for a road trip this summer before she goes away to college. I have road tripped before in both a leisurely and speedy manner and this trip will have components of both. I am looking for some feedback on budgeting specifically food. We have a little more than 3 weeks and it can be either July or August. I also have an SUV that gets 34 mpg on the highway but you can sleep in comfortably with the back seats folded down, so we plan on sleeping along the way at some truck stops.

Start NJ
Day 1. Travel to Niagra Falls, NY area, camp
Day 2. See Niagra Falls, sleep at truck stop out side Chicago
Day 3. Shedd's Aq., sleep at truck stop out side Des Moines
Day 4. Drive to South Dakota, camp in Wall, SD
Day 5. Visit Rushmore, drive to Sheridan WY
Day 6-9. Yellowstone!! Drive to truck stop outside Spokane.
Day 10. Arrive Seattle, check into hostel, Underground city, etc
Day 11. Ferry to kingston, camp at La Push, WA, hopefully catch an hour or two of surf
Day 12. Surf a bit in the morning, dinner with former in laws in Portland, sleep in truck stop north of Eugene, OR
Day 13. Camp in Klamath National Forest
Day 14. Wander down PCH, stop in a motel when we get tired.
Day 15. Arrive Monterey, check into Hostel, check out wharf.
Day 16. MB Aq. Sleep in Truck stop outside Bakersfield.
Day 17. Arrive Las Vegas, try not to hurl (this is something my daughter just really wants to see), Stay in a hotel.
Day 18. Camp at Grand Canyon, AZ. Take pictures.
Day 19-20. Visit family in Albuquerque, NM
Day 21-23 ish: Head home via major highways, no sight seeing planned. Mix of truck stops and motels.

We are planning to only buy one sit down meal a day at a cheapish (but not fast food) restaurant, and eat mostly out of the cooler or use the camp stove. Any idea how much I should budget for food?