This is 1953, Barstow, CA. A group of desert kids heading up to Idyllwild for summer camp. This was an acceptable form of transport back in the day! I see my 2 cousins standing at the back corner, I'm in there somewhere. My mom usually went along as a counsellor, that's her standing in back of the truck, my dad drove the truck. The trip took several hours - and someone(s) usually got sick.
I rode like that once with a bunch of kids but not the distance or amount of time you did. I was at a scout summer camp and we took about a 45 minute trip from camp to a pool. Most of the trip was on a bumpy dirt road from Holcomb Valley to Big Bear Lake. No one got sick but we did get bumped around a bit.