Unity has a lot of tools out of the box and pieces you can purchase and license to put in a game. I would start there. I know godot is getting a lot more in the way of usability given unity's f-ups lately but I haven't seen that engine at all

I somewhat side with the person saying the kid may not entirely want to learn to code but make a game with the parent. I remember those days, the idea of using a computer to make something was beyond me but I made plenty of games on paper.

If the type of game fits, and I think now if the interest is truly in playing the game you make and having it come to fruition, I would scale it down as much as possible, make simple assets, then plot it out in tabletop simulator before making it an actual physical board game.

I've seen plenty of tutorials of Godot on YouTube, but maybe nudge him towards 2D first using Gamemaker or something? I don't know if 2D is necessarily easier, but I'd assume it is. I'm no expert so take with a grain of salt.

If you were comfortable with it, you could use python's pygame https://github.com/pygame/pygame/

I'm not sure how advanced of a game can be made in pygame, but you can definitely create some basic games in it.

After that would be godot https://godotengine.org/ or maybe unity but they seem like they might be on fire or something. But that would give you a full game engine. I believe the engine would allow for a more powerful game to be created.

Both have a good community and documentation, good luck and have fun!

You'll want to run with Unreal or Godot, or if you're feeling a bit indy try the Bevvy game engine, which is built in rust, and the crab holding a Glock to my head insists that this in of itself is a highly attractive feature of the engine!