http://www.dailymotion.com/video/x5iin1_dungeon-party-preview-trailer_videogames
Found this on the site of the developers for "Blood Bowl" -- it's a free MMO, that reminds me more of Gauntlet than WoW, but it has some similarities to WoW and other MMORPGs so it might be a great pick-up game and perhaps even kid friendly... (I love the bright cartoony colour scheme)
http://www.dungeon-party.com/
Free2Play, just released to Steam in March 2013.
http://store.steampowered.com/app/215870/
basics of how to play
http://www.youtube.com/watch?v=MJhpUYRn0n0