Ideally, it would not be a roblox game. I personally would rather not make a roblox account at all. And I want to be able to save progress. I don’t usually end up with unlimited time to play games with him and such. But the game is mostly simple. It co-op, and he likes it.
I can’t think of any short playthrough games off the top of my head, but Valheim might work if you’re open to something longer.