Sorry so late on the response:
Kirbys Epic Yarn.
Easy, multiplayer, bright, cheerful, and suprisingly fun. But at the same time not too tough to play. Very little Waggle in, but enough to know your playing a Wii, just not enough to ever become a pain in the butt or get in the way(simple stuff like shake the controler to have Kirby do things on screen).
BTW, Kirby Return to Dreamland is a bit more complicated and not as beginger friendly, imo. I like Dreamland better because it plays a like the SNES one and feels like its sequel. But in Dreamland you have more dept and layers to not only the gameplay but the way the game was laid out. And it is harder.
Other then that, Wiiplay, Wii Sports. Almost any of the Mario sports themed games. Mario Kart if controls aren't too much of an issue. Depending on the age and gender Smash bros. And of course Mario Party.
Lots of things to pick on the Wii. Esp if your goal is same room MP pick em up and enjoy em games. Just stay away from most games published by ZOO, they are terrible, the zynga of Wii publishing.
Just buy a Kirbys Epic Yarn. Trust me.