I think you should first ask your kids what their favorite park is, and then pick one of the resorts near that park. If they're young, it seems like the Magic Kingdom is a given, but who knows, maybe it's one of the other 3, and they might like being able to walk to those parks by staying at the Boardwalk Inn or Y&B.
If it is the Magic Kingdom, I'd think Wilderness Lodge or Contemporary. Monorails rock and everything, but I think if I were a kid, being on a ferry, where you can always get to the front of the boat and see the MK slooooowly get closer has got to be as exciting as you get before getting involved with crushes. And being in the Contemporary, with monorail OR walking options, has got to be convenient.
I'd also think about getting the planning DVD, and exploring websites that show pictures of the hotels online. Let the kids help choose where they'd like to stay, unless you think they'll get in a fight over it.