Any Wii enthusiasts out there?

We're gonna ask Santa to bring us a Wii this year but we anticipate that he'll have lots of questions.  These things are not cheap and there's a mind boggling amount of games and accessories.  I spent about an hour at toysrus yesterday and finally gave up because there's just too much to try to figure out and there's NO WAY I'm informed enough to just start throwing things into my cart.   So I'll start by taking my questions to the experts.  Um....that would be you guys.  :)

• Do these things ever go on sale?
• Is there one type of system or is there a "plus" or a "2"?  If so, what's newer (best?) and do all the games work with any system?
• How many controllers do we really need? 
• What about chargers and other accessories?
• Do you need something special to use this on a big flat High Def TV?
• What games will my 5 year old girls really like? 
• Anyone have a Wii Fit (and use it?)

I might have more questions later!  Thanks for any advice you can give us!