There's no age or height requirement for the Safari. The ride is VERY bumpy, though. It is highly recommended (in fact, your tour guide will announce this) that you place small children in the middle of the seats and away from the open ends of the benches. If you are the first to enter your row of the vehicle, have the two adults enter and then put the infant to the right of the second adult. If you are the last to enter your row, put the infant to the left of the first adult. And then whoever has the infant next to them, hold on very tightly. There will be more stops and sudden starts than anything.
The Safari is one attraction that my two year old grandson can go on and I can't because of a medical problem.