There is an "unpack" section in the Settings which seems like it might do what you are looking for. I'm unclear if it will leave a copy for seeding though, as I've never used it.Is there something I could install on Whatbox that will automatically unrar (or just copy if it isn't rar'd) downloaded torrents into a different directory? I have autodl-irssi setup to grab the torrents I want and put them into separate directories based on who the download is for, hoping to be able to further handle the files automatically so I can just setup some ProFTPD accounts for family members, giving them access only to the torrents they've requested.
The Autotools section is what I use to make a copy for Dropbox, which then syncs with my home computer while keeping a copy for seeding. I'm not sure if some combination of those two things (unpack and autotools, not Dropbox) would work or not, but if you're setting up FTP on their computers already, you could perhaps work something up with Sickbeard or the one a_skeleton_03 mentioned recently, Sonarr.