Haven't tried this with kids yet, but "coloring computers" might be a cool thing.

You can find it here: Coloring computers: non-electronic computers that work when you color them https://ipfs.io/ipfs/QmYz7DPRWypGQcbAHr7Mi8EKB6ntSPsEnUsCXbA...

And the recent HN discussion: https://news.ycombinator.com/item?id=31393501