I would have to respectfully disagree with your suggestion that a 4 wheeler might be something to try. My one stint on a 4 wheeler was a disaster, and if I could give one reason I would say it was because though it may share similar controls to a motorcycle, the skills are in no way similar. Basically because it looked something like a motorcycle I believe that I was trying to use subtle inputs, including countersteering, when to properly ride an ATV your inputs have to be anything but subtle. I was trying to dance with it when I should have been trying to wrestle with it.
It anybody on the board has extensive experience with 4 wheelers and disagrees, they might be right, but from my very limited experience I’d suggest sticking with the previous advice of a dirt bike or a scooter for some experience.