[belthesar]

I had my grandmother running on Linux since 2008, and she loved it. She wasn't gonna get a virus, she didn't have root/sudo capability on her user, which meant she wasn't going to break anything, and she had ad blocking in her browser. She was told two things: "1. If something wants to install something or update something, say no. If it keeps asking, call me. 2. You can't break this." This removed the fear she had using a computer, and went from "too afraid to turn it on lest she hear the sighs and frustrations of her now late technophile husband" to "doing everything from social media to online shopping". The last machine she had was an Asus Chromebox I bought her when the machine she was using was just not able to keep up anymore. She used Google Apps for word processing, Gmail for email, and had a ball.

Sibling commenters have it right - if a computer is an appliance to them, then going for the simplest, least likely to accidentally mess up option is the best one.