In short, your interest at Four Seasons Residence Club includes three weeks in Vail every calendar year as part of ownership; this is called your "Primary Use Time." It includes two assigned "Platinum Weeks" during the prime seasons, one winter and one summer. Your two assigned weeks rotate every year based on the Reservation Group letter that you purchased. Additionally, each owner receives one "Gold Week" that they may  use during the other 28 weeks of the year. (See calendars below.) 
You may also trade your time with the other Four Seasons Residence Clubs and reserve time in addition to your three weeks on a fee-for-use basis. If Four Seasons Club program does not sounds like it will work for your family, there are other fractional properties in Vail that I would be happy to introduce you to. Please contact me for more specifics and additional information on this property or others.