Just get an old computer. Old computers don't die - their users do. You can get a nicely specc'ed ZX Next ( https://www.specnext.com/ ) or Amstrad CPC6128 for the budget, or find an old C64 and deck it out with some solid-state storage (actually do this for all the machines, they all have it now). My kids learned hacking on an Oric Atmos with a Cumulus drive (SD-card storage), which was just mind-blowing to see and a…
+++++ This is what I always imagined I'd do if I had kids, and I think I'd love every minute of it. Did your kids get bored with those things when they got a look at an iPad? Or did they understand what they were looking at?
At first they were all "oh this is crap, look how big the pixels are! " but then after I typed in a 10-liner, the wonder started and they haven't complained a bit since, besides the time the power went out and nothing was saved .. but even that was a valuable experience, because my kids finally were able to properly elucidate the difference between a file and a folder, and in fact had a much better understanding of what a file is, in the first place .. a problem many still don't quite resolve today.
Just go for it. Even if your kids ridicule it, you'll have fun. :)