It falls short on your 3d request, but for someone new to things I'd go down the pico-8 rabbit hole.
There are some really spectacular (given the limitations) 3d games, but they're the exception. However, the IDE is built-in, it's basically lua, and you can load/view/edit the source code for all the published games.
My 9 and 12 year old have both played a fair bit with Pico-8, and while the music and sprite tools are neat, I think there's a lot that it leaves on the table. The Lua environment is a fun puzzle for seasoned developers to reason about how to make the most of it, but for a novice, stuff like physics, collision detection, and an entity system out of the box is more like the right starting point. You need a lot of boilerplate to get a sidescroller off the ground in Pico-8.
I think for a newcomer this is where loading an existing game (like Celeste...) and just changing sprites or updating logic gets you some of the non-built in features for free - but at that point you're more modding someone else's game more than creating your own. I can see how that path could be a non-starter for some folks (no matter their age).