The OP said that it's a leased car that will be returned in May, and that it should still be in the mileage allowance even with this trip. So basically there's no worry about wear on the car. I haven't thought about returning a leased car since my dad returned one 30 years ago, but I'm not sure if there's any tire requirements either other than adequate tread to move it safely. Doing some research, and some have bought used tires cheap to meet the requirements for return.
One can save on food with a cooler and sandwiches. It would also save time not having to track down restaurants. However, as someone who went backpacking for several days, it's nice having a hot meal every now and then, especially prepared by someone else.