Ummm.. the sports games are pretty safe. You can probably pick up Rock Band stuff pretty cheap now since they're in such little demand. Hell you can go to a local goodwill/donation store and likely find some cheap used musical instruments for it. The Just Dance games may be winners. Just look at Amazon or Gamestop and it won't be hard to find some age appropriate stuff.
If you want stuff that ISN'T age appropriate I'd suggest No More Heroes and MadWorld.
Well I based it more on my 25+ years of video gaming experience and what I would find appropriate for them. I have 2 kids but at < 3 years old and a 6 month old, it's probably going to be a while before I introduce them into that form of entertainment. Of course if it were up to my wife she'd see to it that they have NO exposure to it whatsoever..