My Mum's 90 and had her iPad for several years, and is far happier with it than she ever was with her laptops.
The only advice that I can give is that (if you're the person they call when they have a problem) is either to buy one for yourself or get good at trawling Apple faq pages when something doesn't work. Mum's has needed the network settings fully reset three times now, which is just infrequent enough to make sure that I've forgotten how to fix it when it happens again.
If you're setting it up for them, write down all the login passwords and network stuff and take that away with you. (I use evernote so that I can get the info anywhere easily).