I started putting together a "book" when I was teaching my 6 year old a bit about coding. It uses a BBC Micro emulator and BBC BASIC as the intro language. Never got around to finishing it... http://c4k.rabidgremlin.com/
I did the coding but it was his concept, he did all the graphics (scanned pictures he drew), the font (generated from his handwriting) and sound effects (that's him making all the sounds).
He also built the levels and used a music generator to create the background music (not in the version that is on the website yet). This was all done in Unity with a lot of prefabs to make it easy for him to build the levels.
I'm totally going to introduce him to PICO-8 (see link below) next to see how he gets on :)
I'll see what I can do re sharing the source code...
He is a pretty awesome kid :)