Two years ago when Rock Band was released, we gave it some serious consideration for a family Christmas gift. But we ended up giving the whole plastic instrument craze a pass until this year where we used some gift money and took advantage of the post-Christmas sales to buy Beatles Rock Band. The big advantage is we "know" most of the songs.
And we're having a blast. C is getting better banging on the skins, and I play bass while K handles the vocals (although we might swap). We've worked our way through the story mode (on easy for the most part) already, so now we'll probably explore and see what else the game has to offer. We might buy some DLC (like the Sgt. Pepper album) and maybe even one of the other games (since we have the instruments).