I switched my parents to linux during the gnome 2 days and have given them a consistent environment ever since (kept them on mate).

It is true, they could not do this themselves and sometimes my mom can test my patience, but this is the way if you can do it. (Hint: get a remote desktop with shared view working first :).

Really, the stronghold for windows is their office suite (other family require Word/Excel for work), enterprise domain integration (work to home pc familiarity), and, to a weaker extent, gaming. Gaming is why I still keep an install of windows on my pc.