My plan for my kids when they're old enough is they'll get Linux laptops to play with, and the option to use Windows if they can figure out how to install it for games.
Because what I want to encourage is understanding how the machine works, that it is a machine and that it can be manipulated, since my most important formative memories when I was young was that my dad was writing his own software to run his business and that core message was something me and my brothers spent a lot of time emulating as play.
Plus changes are immediately visible, kids patience being what it is.
You could also probably stick them in DOSBOX.
You'll be doing just fine if you lay down some boundaries for them limiting the time they spend on any one activity. Bonus points if you take part in those activities with them. :)