Don't overthink this, it's a kid. She/He would not be yet biased like you or your surroundings. About wife - I don't she would be against teaching kid how a computer works, maybe you explained it so she heard "hey can our kid spend more time in front of a screen and with my geeky thing" :D.

I have a little smart sister (now 9 yo) that use Linux, it started with her making a mess on Windows login (parents laptop) so I asked if she wants "her own space", but instead of new account I installed whole Fedora on second partition. Why Fedora? Because It works and looks nice, there really is no need for "educational", just install education programs on top.
There are basic parental controls in vanilla Fedora, but honestly there turned out to not be needed, she don't hook too much after first shock of tech and like two cries she learned to stop when we say to stop, at least most of the time. Depends on the child, I suppose some really need a timer, that's up go you, nothing bad with that. I have showed her some games too, she loves everything Tux. I teach her how computer works this way, showing more and more programs with time and every new icon of Krita, GCompris, Goxel or Scratch is new great thing. She has Windows at school, but everything works on her space too. Well almost, LibreOffice does not has 'online cliparts', so instead of arguing with 9 year old I told that program at she uses at school is not available on this OS (after a while of teaching she knows OS is something something wow the desktop looks like :D) and showed how to download search copy from the browser. With being honest and just responding on every little childlish curiosity question she already knows more about computers than her mother. I just made it normal for her, as after using Linux for years it is normal for me.