Hi
The Wii Sports games are a good start and come with the console.
If you get Wii Play you get a remote and a set of games (more training exercises for using the remote) and are fun.
We have just had topspin3 (as*a) for �25 a brilliant version of tennis, we also have Mario Superstar Tennis, the graphics are exciting on that for all, but not a real real tennis game.
What I would suggest is a second numchuck.
As said before a charging station with some high power recargable batteries ours uses AAA and we got 1000m/amp and they will do 3 rounds of Tiger woods golf plus a few games of Wii bowling.
Hope that helps.
L