Smugglers Notch, Vermont
Just say "Family Ski Resort!" as loud as you can. Numerous kids programs, huge slope-side child care center, Teen Center and Teen Alley for two age groups, teen boarding programs at night*... Fun off the slopes includes snowshoeing, ice skating, tube-slides, sleigh rides, horse-riding... or how about an art workshop? Plus bonfires, family games nights, an indoor FunZone under a big bubble with Bouncy House, minigolf, lots more.
One of Aspen's four ski resorts (-- one lift ticket gets Snowmass, Aspen, Aspen Highlands, and Buttermilk), connected by a free shuttle. Snowmass has a whopping 4400 vertical feet, and a giant new children's center; for older kids 12 to 19, Too Cool for School makes groups by age and skill*.
Solitude Ski Resort, UT
Solitude Ski Resort - 28 miles from the Salt Lake City airport-- has kids Ski School, and an attractive little "village" of lodgings plus shared leisure facilities (mini-theater, outdoor pools...)
Steamboat Springs, CO
Another of Colorado's best-known ski resorts, Steamboat is 147 miles north of Denver; has plenty of activities for kids age two and up; kids-only terrain and lifts; terrain park, and night-tubing; and frequent Kids Ski Free and Rent Free programs. Great town, as well; and hot springs, too.
Kidz'n'Snow tells you all you need to know about family skiing at Sugarloaf. There's a tubing hill, Outdoor Center, terrain park, and -- for advanced skiers-- the only above-treeline skiing in the east, at Snowfields (all double-diamond runs.) Sugarloaf is in the sticks, so you might want to buy groceries before you drive to your condo.
Sun Peaks Family Ski Resort, BC
The Okanagan area of BC has that magic phrase "champagne powder" (light dry powder snow), plus four family-friendly ski resorts. Sun Peaks Resort is all about family skiing, with three mountains that are easy to navigate, handy little village, and off-slope snow fun from dog-sledding to sleigh rides to snowmobiles.
Sun Valley, ID
Sun Valley's gateway cities are Boise Idaho and Salt Lake City, Utah. Ski and snowboard lessons for kids; School daycare for ages 4 months and up. Check web site for latest.
Telluride is one of Colorado's more remote ski resorts, but visitors get a beautiful mountain town (National Landmark Historic District) plus stunning scenery. The town is at the mountain base; mid-mountain is the upscale Telluride Mountain Village; a free gondola links the two, and both have ski in/ski out lodging. Mountain Village Nursery takes wee kids age 8 weeks to 3 years.*
Vail is a well-known Colorado ski resort and it is big: the biggest single ski area in North America, with over 5000 acres of terrain. Vail has nightlife, kids' programs, a tube park with covered lift, and legendary "back bowls" loved by powderhounds. Vail is just a few miles from Beaver Creek: lift passes are good at both, and also at Keystone and Breckenridge, which are also owned by Vail Resorts.
Top-ranked ski resort with Kids Adventure Zones (a magic castle, secret forts, etc.), Children's Learning Centre, adventure camps, "Ride Tribe" for teens. (Plenty for non-skiers too; Whistler wins lots of "Apres-Ski" awards.) Whistler-Blackcomb is also notable for its long ski season (into June), and awesome numbers: a mile of vertical drop, highest in N. America; and over 8000 acres.
Winter Park, CO
Closest ski resort to Denver; family-friendly, reasonably-priced.
For more suggestions for family-friendly ski resorts, see Kidznsnow.com.
*Always check web sites for updates!