I suggest Unreal Engine, 11 years is old enough to follow tutorials on YouTube. I think I was at around this age when I played with Game Maker on Commodore 64.

There's not much coding required in UE, but there's some learning curve that's for sure. Having an instant feedback however is really good for learning.

I would also suggest https://www.rpgmakerweb.com/ which is a good for 2D RPG games, there are quite a few variants of they they released.