Film, in its own airtight plastic box, goes in the cooler. With the beer and/or wine.
Cold beer and/or wine = cool film!
New film, which I usually collect on bike/train in the Big Smoke, gets stuffed into a small fold-away cool-bag for the trip home, Camelbak-class.
Camera travels 'as-is' in the car: no special protection. I take the cameras with me whenever I've stopped and the car is not in my line of sight.
Methinks that up north where you Americans are, it is very blazing hot and stuffy at this time. Downunder is getting a blast of cool air and rain. Nice for rainforests...