I would agree with others about no age limit. I would say a size limit is needed since the vehicles have 5 point harness. Kind of like roller coaster rides at Disney or Universal etc 42" min.
I believe kids can go on U drive with a parent driving. Those vehicles have 3 point "shoulder" harness.
Their website says people of all ages. The bucket seats have a 5-point buckle system but if your kids are on the smaller size, you might want to reach out to them directly for advice.
If your kids are a bit of a thrill seeker, they'll love it!