Ask HN: How have you shared computers with your young child (~3 to 5)

My kids are not quite screen time age, but at some point will be. I'd like to give them an interesting computer experience instead of just plopping them in front of an iPad with some media.

When I was a kid I had fond memories of exploring the file system, figuring out how applications worked, playing with Kid Pix, Paint, and a few games (roughly Apple IIGS, Macintosh 2, through iMac + a Windows XP desktop).

Do you have any fun old laptops or device you've got lying around that you've used to introduce kids into a desktop environment?

Any and all recommendations welcome :)