Not naming names, but someone took their almost 9 year old 51" tall son to Secrets of the Empire at the Void in Disney Springs. The son loved it so much that he asked to do it again immediately, and, in a moment of weakness, his dad agreed.
It was slightly awkward to put on the gear because it is hanging on a hook that was too tall for the 51" tall boy, but the Void workers were very helpful. The gear is slightly heavy, so the Void workers advised that if you need help or get tired to just raise your hand while you're in the experience.
I mention these slight inconveniences just to be transparent and give others information. By slight, I mean slight, negligible, almost non-existent. The boy had an AMAZING time and named it as one of the highlights of his trip. He didn't have any complaints about the experience.