Hi - what about just a variety of finger foods. It may not feel like a traditional dinner but with the right "snacks" and enough of them - it can become dinner.:
- Cheese slices / meat slices (protein)
- crackers or little bread rolls (grain/carbs)
- plain cooked pasta that she can just eat with her fingers (grain/carbs)(the smallest that you can get that she can still hold so she doesn't choke).
- veggies like grape tomatoes, cooked carrots, broccoli, peas, cucumber sticks, etc. (veggies) Just make sure to cut into small pieces even for the grape tomatoes so she doesn't choke on it in the car.
- fruit like cut up apple slices or watermelon for desert
Another suggestion is sandwiches. I have one of those sandwich makers which are awesome. You can make some kind of filling and make a bunch of sandwiches. You don't necessary even need a filling as such. You can even just put in some ham and cheese slices. Its great because the sandwich maker essentially seals in the edges so its not as messy as other sandwiches might be.
Good luck and safe trip!!