Gamemaker if you want no code. It's free if you're not planning to release games commercially. You can add code later if you want custom behaviors that gamemaker doesn't include out of the box. 2D only.

Godot if you want coding. Coding is required but it uses gdscript which is a python inspired language. The editor is also batteries included, so godot.exe will include everything you need to make a game (aside from assets, but even there some plugins can help). 2D and 3D, but 3D is not "AAA" tier.

I honestly recommend you go for godot. There are tons of tutorials out there to create all kinds of games, specially if it's something basic. It's what I wish existed when I was 11 and had tons of time to mess around.

I'd say look up a quickstart tutorial for both and check if your kid likes any of them.

I see lots of recommendations for niche/toy engines. I don't recommend those because it'll be hard to look up tutorials for them. Having guidance in essential. I also don't recommend your kid get to roblox, sure he might be able to make some money or get lots of attention, but having external motivators can be very detrimental.