What extra sort of stuff do I need when I buy a Wii?

Here’s the thing. I’m personally opposed to video games—for the only reason that I tend to get addicted to them. But my wife and daughter really want a Wii. My wife wants it for exercise and my daughter for something called Dance Party or something to that effect. I’ll probably play with it a little, but I’d limit my time.

So my question is, what do I need beyond the basic set and the software? My wife went to Target and was a bit overwhelmed by two aisles of Wii stuff, and I don’t want to get too much or too little stuff. There may be a game or two that the three of us would play together.