In terms of keeping him safe online look into some content filtering for the whole home network, either paid or self-hosted.
Projects that act upon physical stuff are the most rewarding. Something simple such as building a simple Python script that interacts with a smart home API and turns switches on/off or changes light colors around the house are relatively simple and require no hardware/mechanics if you're not into robotics, soldering or circuit boards.
You've got a great kid :)
For anyone using Figma, there's a free open source alternative called PenPot that's quite decent.