Don't toss them. Why not put them in a cooler in the vehicle your driving?
This is what I would do also. In fact, I take a film cooler when I travel for my fresh film. You can get one that plugs into your car, or use the cold packs instead of real ice. It will keep the moisture down. I don't think you'll find them that fragile. My Grandmother's negatives from 1900 on were stored in the farmhouse attic for years and they are fine. My Brother printed a bunch of them a few years ago with no problems.
Moma don't take my Kodachrome away!
Oops, Kodak, of all people, did!