Seeing as I feel that I'm backing up well enough at the current moment, here's what I would do:
I would use WHS to build a backup server for my parents and little brother. My lil' bro' doesn't know the real value in backing up his school work and essays just yet. So, it would probably be better if he didn't have to learn it the hard way.
On the other hand, my mom needs to backup her photos really bad. In addition to the WHS copy serving as a backup server for documents and photos, I would add an additional layer of backup to the photos by having them copied to a paid backup server (I think it is 50 GB for 5€) just to be on the save side.
For my dad I would add my own coded program that uses X10 devices to turn on and off the car engine heaters at exact times and not leave him to have to remember turning them on. (Maybe event turning the heaters on an hour earlier if the outdoor temperature is below -15 degrees Celsius) The same X10 could also be configured to turn on the outdoor lights when it gets dark (which is quite early now) and maybe turn on some lights indoors as well.