I'd throw out two alternatives:
1) Breckenridge. I may be biased, since I work weekends there, but I've generally found that we have the best ski school in the state (though I've had great experiences with the Winter Park staff, as well), and we easily have the best learning terrain in the state (the slopes tend to be well differentiated, making it easy to stay in a 'greens only' or 'blues only' area, without having to worry about making a wrong turn). There's a Marriott owned property at the base of Peak 9 that seems to work as a true Marriott most of the time (rather than more of a vacation property thing).
2) Given the age of your kids, if they've never been skiing/snowboarding before, I'd agree with VickiSoCal to a degree. If they're just on the bunny hill all day, you might as well pick a bunny hill near a preferred hotel (whether that's Vail, Winter Park, Breck, whatever) at a resort you'll enjoy being at.