Even with the iPad there was some technical support needed. It wasn't responding to touches once, so I jokingly asked her to use her "good thumb" and it worked. She had been holding the tablet and her "good thumb" was touching the edge of the screen, which caused her taps to be interpreted as a two-finger pinch.

I don't think that a PC is a good choice here, personally. From talking to others, it seems like the elderly are generally unwilling to learn something new and see it as a roadblock.. until you find something that they like and hook them that way. For my grandmother, it was solitare and other card games. She was blown away that she could play all of her favorite card games on one device and that she didn't have to shuffle cards or anything like that.

Old people and toddlers are very similar and if you make learning fun they're so busy enjoying themselves that they've not realized that they are learning at the same time.

Best of luck, OP!