Pick an adult solution and sit with them to provide adult guidance. You are at the stage where your relationship with your child becomes peer to peer.
If game programming stays their jam, you will be learning game programming from them in the blink of an eye. It's joyous and wonderful and only gets better.
Sure you will miss them being a small child, but you will know an amazing adult. (and they will always be a small child sometimes just as we all are).
The platform doesn't matter. Your relationship does. Good luck.
My approach with my kids has always been "don't dumb it down". They may not be into programming, but at least they'll be exposed to it.
By giving them the 'easy' version, you are putting up barriers that don't need to be there. Kids are smarter than many adults give them credit for, but again, it depends on the kid.
You would be teaching a soon-to-be-adult about the adult world. The game engine is entirely incidental to developing a peer to peer relationship.
Their interest in spending time with you will diminish. That reality is the one to optimize for. Recreational interests come and go and come back sometimes. But most don’t stick.
Learning Unreal Engine with your 11 year old is possible, but not for more than year.
I have done this, it can work with some kids, still, its too much work.
At this age, I think it is more important to keep them motivated and find ways to use their creativity than to get them through the pains of debugging and learning too many technical concepts, even simple details like learning about image formats, how to reference them, case-sensitiveness are just obstacles against meeting their goals.
I feel like we don't give kids enough credit. Game devs who started in the 70s and 80s learned BASIC and all the technicalities of their platforms back then, some eventually moving to Pascal, C, or Assembly. The platforms had fewer variables back then (code running in real mode, your machine was identical to others of the same platform), but kids were still able to learn the minutiae of the Apple II or Commodore 64.
Pick an adult solution and sit with them to provide adult guidance. You are at the stage where your relationship with your child becomes peer to peer.
If game programming stays their jam, you will be learning game programming from them in the blink of an eye. It's joyous and wonderful and only gets better.
Sure you will miss them being a small child, but you will know an amazing adult. (and they will always be a small child sometimes just as we all are).
The platform doesn't matter. Your relationship does. Good luck.