I'll second Headmaster (yes, I mention Headmaster a lot since it doesn't get brought up much). My wife and I usually use it to demo VR for people that aren't big gamers. It doesn't use the controller at all once you start the game, it's just looking at menu items and moving your head to hit balls. The demo on the first demo disc is perfect since it includes the tutorial, but the full game is fantastic and on sale.
Also, you might consider Hatsune Miku: Future Live if you think they can handle voice-synth jpop, or would find a concert in VR worth the trouble, or not be creeped out by the whole thing. Iirc you have to buy one of the DLCs to watch anything. Idolmaster VR is a touch creepier to me at least, and it only plays one song at a time so it feels less like a mini-concert and more like a really expensive demo. The Miku concerts have a lot more special effects iirc, which helps. I think you can turn off the motion prompts and just watch the songs in Miku.