I'm mostly thinking "Big brain academy". Perfect for the environment.

(I'd mention "Bully" as well, but afaik, it's not a quick "pick 'm up and play" kind of game. Or gives the correct attitude

).
Further...since it's unknown who will get the wii, it's best to go with neutral games that appeal to non-gamers as well. So I'd go with...
Wii:
Boom blox (surprisingly addictive)
Wii play motion (I'd stay away from wii play unless you REALLY need a regular wiimote)
Wii sports resort (especially if you have multiple wiimote+ thingies lying around)
Mario kart wii
Wii party (doesn't get enough credit. IMO this one's way better than Mario Party 9).
Just dance 1/2/3 (this is a MAYBE...either this'll be a favorite among the scholars, or it'll be passed by everyone. It's probably best to pass it unless you have at least two people there who actually want to play it).
Wiiware:
Bomberman blast
Driift mania (you can even go up to 8 players at once, if you have enough nunchuks or other devices)
World of goo (okay, this is single player...but it's very fun to watch others play)
tetris party (you could go with the wii version as well, but they're identical).
@[member='TDWP FTW']: those microgames are actually 5 seconds long, which makes them mostly a matter of wits. There are some longer ones in them, though. And of course multiplayer ones.