My son is a bit of a Minecraft addict and has recently got into Minecraft customization (that's adding his own assets to the game).
It's opened up so many horizons for him – 3D modelling, games design, graphic design, audio, coding, not to mention a stronger interest in maths. We had a conversation about colour theory the other day – something he's never mentioned before – because he's learning how to make his models look better. Last night, I had to pull him away from the computer because he wanted to stay up coding.
I've written about some of the tools available for Minecraft modding – Blockbench, MCreator… – on my nascent blog: jllyfsh.com/articles/top-minecraft-tools/
They're not complex tools. They're free and worth a look at – especially if your kid spends all day playing computer games and you think their creativity's going to waste.