We really enjoy our Wii.
Our girls LOVE Just Dance. That really gets them moving the most.
A Mario Brothers game came with ours and after a year of not really playing it at all, that's all one wants to do. That one is a sit down game. Another game the girls are very active with is Wii Resort Sports. It has a cool sword game where you chop items up like cupcakes, diamonds, eggs, etc. You have to chop in the direction the arrow shows. That's been a favorite. Really, with the Wii, we've found out you can be as active or not active with it as you want. We've played golf sitting in a chair and just moving our wrists. But that's us adults :-). The kids are usually very physically active and love being physically active with it.
I had thought about the Wii Fit, but I haven't decided on that yet.
It's well worth it to purchase a charger. With the wrist straps on, ours is sometimes harder to get them to click into place, but they make different ones. That saves $$ big time so you don't have to purchase batteries all the time.
One thing to note though, is you definitely have to watch out for each other while playing. You get so engulfed in the game that you can accidentally hit the other person in the head with the remote and if you're swinging pretty hard to do something, (baseball or tennis for example) it can really hurt. We've had that happen on a few occasions. So, hopefully, you have plenty of space for each person playing.
Hope this helps a little.