Casey rode in my CJ all the time, mostly because it was my only means of transportation until she was 8. We really didn't take her on trails until she was 2-3, and only with neck support. Our biggest problem was keeping her from frying in the sun - no AC means no top in the summer. The summer she turned 5 we went to Moab and she rode in the back of a YJ through every trail we went on, although something about it made her go to sleep. She slept through more scenery when she was 5 than a lot of people see in a lifetime!