>>399102527
Start them with VR games that require no locomotion.
Then onto games with good locomotion safety features like holoports.

Half Life Alyx is a good introductory game but will also make other games look dog shit in comparison. So reserve that for when he is starting to lose interest.

VRchat worlds are good to start with as long as you use holo port locomotion option. Try Treehouse in the shade world and Putt Putt mini golf world.