http://waffles.i2p/blog/familiarity.html
If we take a look at how people use their computers, they have a web browser, a file manager, and a settings page for the most part. If it can connect to a printer, save a file, view an image, and play a video, they're generally pretty good. I know you're going to expect me to say gaming on Linux is also viable, but for games children play outside of Steam, I'm not so sure.