Hi Happy girl,
My son and daughter both got a wii, son was about 13 or 14 and never really used it much at all, he would tend to use the computer games much more.
My daughter got one last Christmas and also used it very little, would much prefer to play computer or ds but it is fun if they have friends around.
We set it up in our sitting room because we thought she would be more inclined to use it when it was more visible and also maybe include us adults but it got forgotten about very quickly. I got the wii fitness game but found it a bit frustrating to use as it often didn't recognise my moves.
I also found the sensor bar that sits on the top of the telly a bit flimsy and often fell off the telly and broke, we had to replace ours a few times which is a bit of a pain, we have since read from the net that if you use two night light candles on top of the telly it works instead of the sensor, we've tried ot and it works.
Pricing around on the internet is well worth it, you can buy it on it's own or as a bundle with games or extra nunchungs, so if you do go ahead decide what games you want and how many will play it at the same time. It's more fun with a few people so you will need extra nunchungs. Places to price are argos, tesco, asda, smyths, play.com.
Hope this helps.