Programming

I can help a bit with software. I tried Godot a while ago, didn't personally like it, though I do recommend your son tries it, as it does work with Python and won't require learning a new language. Also heard it's beginner friendly. That's how I started at least.

Unity is my recommended game engine - it's more versatile and has quite a community, so it's easy to find answers to almost any questions your son might have (and trust me, he will have a lot). It does require learning C# though.

For big AAA games the answer is Unreal. It works on C++. Can say much about it, I haven't tried it myself, but I did hear it's has a bit of a steep learning curve. Would recommend this one only if your son becomes very invested and will have made a few games already.