I once tried to get my cousin, 9 at the time, to record an UTAU. It was a CV reclist, and she liked trying, but kept complaining that the reclist was long (lol) and that she wanted to skip to the part where she could use her vb. When she did, she wasn't very impressed with the robotic results, and when asked if she wanted to try a different way of recording she became very enthusiastic, but we never got around to it.
My little sister is about to get her own laptop. She's 10, and she is VERY eager to begin with Vocaloid! When I told her about UTAU and showed her mine and some videos of how it works, she became very, very excited to try UTAU. So I'll have to take some time to lend her my Yeti (not alone, of course) or buy her a microphone to get her on her feet. Probably just a standard Logitech microphone to start.
So yeah. I've tried, and will try again.