Steamboat and Winterpark are both great resorts, but there are others which may cater more to beginners (Steamboat is also a total pain to get to from Denver). From the top of my head I would recommend Vail resort to you. Easy to get there fomr Denver airport (shuttle service that goes right there (and to all other resorts in Colorado)).
Vail also has fantastic slopes for all experience levels - from the beginner basics, moving up to the blues and 'easy diamonds' and up to the real challenging stuff. They consistently get good snow.
Vail also has lots to do in the area, and with your Vail pass you can also go down the road and ski at Beaver Creek - a fantastic resort, very family-friendly, with lots to do.
So Vail would be my pick, along with Beaver Creek.