Just wanted to clarify something:
There are, absolutely, people for whom thrill rides of any kind are out-of-bounds for life. I seriously believe that there are brain wiring, brain chemical issues here -- I know for a fact that I experience motion and sense of motion in a very different way than DH and DS do. (As an example, even though intellectually I understand that it's not the case, I am one of those people for whom they make those announcements in the Epcot 360 degree theaters to reassure them that the theater itself is not moving -- I absolutely experience that sensation but DH and DS do not.)
What I meant in my comments to the OP (and I am thrilled that her trip proved the point and went so well) is that children do go through a developmental change at around age 10. They understand the world and their experiences in an entirely new way -- the line between reality and fantasy becomes much more clear, they become much more independent, etc. This change can mean that a child who wasn't ready for certain rides before and SAYS he or she is now ready can be trusted and given the opportunities to try. It doesn't mean he or she should be pushed because he or she is "old enough now" -- since it could be someone who will never be comfortable with thrill rides.
Hope that makes sense!