My grandparents are dead, so I can't really speak for them (insert bad bsd joke here), but I know my mother has no problems clicking on the wifi icon in ubuntu. Really, while wifi can be nuisance in some distributions, ubuntu has come a long way. Even a generic acer laptop which one of my neighbors uses, complete with a (reputedly horrible) broadcom wnic, worked out of the box on. While I'm sure there are still some black spots on the linux wifi map, you have to be pretty unlucky to get something which doesn't work out of the box on said distribution. And if you want to eliminate luck as a factor, you can spend five minutes extra the next time you buy a computer, and make sure you get one with atheros or intel chipsets.
While Apple hardware may be excellent, their macbook line is still overpriced by $3-400 compared to a similarly spec-ed Lenovo. This I believe, is the biggest rationale for not choosing apple. If you can get a similar or better non-Apple computer for less price than an Apple, why would you go with the Apple? Especially if all you do is play solitaire and flash games, which you can do on ubuntu just as well as on osx (easier according to my mother, as the dock confused her).
On a side note, as I'm sure some will suggest installing OSX on non-Apple PC's. When I recently installed 10.5.* on my T60, the wifi (iwl3945) refused to work. I don't think the drivers were ready. On the other hand, ubuntu immediately recognized the card and configured it; so I can only assume that the whole OSX "just works" experience only applies to Apple produced PC's.