This could be of interest if it has to be 3D. I haven't tried it myself but Code Combat generally has a series of "wizard style" tutorials.
If he's ok starting with the basics of coding and 2D game development then Code Combat's original Game Development 3 Course Series is pretty good to start with if you want him to go autonomously with out basically having him type out/copy pasting what you are doing.
https://codecombat.com/play/game-dev-1
If they are willing to do 2D and can follow a tutorial I'd recommend microstudio.dev using Lua/Python/JS or Microscript.