When packing food for a road trip, use small frozen gel packs in your coolers. These can fit between layers of food, keeping both sides cold. Keep in mind they won’t last for long periods of time, though. For short trips, trips to the beach, etc. they work great. Check out ones that are made for diaper bags. They tend to be more streamlined and don’t take up as much room.
Some foods that travel well include: veggies like carrots or celery, cheese cubes, apples, bananas, nuts, cookies, granola, and dried fruit. I’m sure you have your favorites. Travel healthy!