Yeah, Boom Blox Bash Party is a pretty solid recommendation, especially for a game that the whole family can play (my wife loves the original). Also, Mario Kart Wii is a must. The game comes with a wheel, but the wheel is basically a cut out that you stick a remote in--you don't need it to play, but I love using it!
One game I haven't seen mentioned so far, but I think it's a great investment, is Link's Crossbow Training. It's basically a Duck Hunt/target practice game, where you can compete with friends for high scores, but I've had a ton of fun playing it. It's not expensive.
You might also *consider* Big Brain Academy. It's not a game that I'd recommend straight-up to another gamer--it's a series of mini-games designed to get people to think fast--but, again, my wife loves it, and as a father you might be interested in checking it out for your kids.
