The Colorado resorts of Summit County (Breckenridge, Keystone, Copper Mountain and Arapahoe Basin) can provide superb skiing given the right conditions. Children are especially well catered for in the first three.
Breckenridge sprawls over four peaks and has skiing to suit a wide range of abilities. Beginners will love the long cruisers on the lower slopes, while advanced skiers will revel in the challenges of the huge powder bowls and steep moguls. The names of the runs often speak for themselves.
Keystone, likewise, has something for everyone, including extensive night skiing. The additions of two new areas has provided some excellent gladed skiing and some open bowl skiing in the Outback and North Peak areas. Keystone also has one of the finest mountain restaurants in the US.
Copper is my personal favourite in this area. It has a wide range of possibilities, enhanced recently by the opening of more bowls. The mountain is divided into quite distinct areas of difficulty, as the further right you go (looking from the top of the mountain) the more difficult it becomes. An efficient lift system ensures small queues. Runs like Copperopolis take a consistently "cruisy" line almost from the top to bottom of the mountain.
Arapahoe has a more Alpine feel to it than most US resorts, being like a mini Tignes in some respects. It's wide open slopes are mostly above the tree-line and it has some frighteningly steep runs (try the Pallavicini slopes) and some accessible off-piste steeps.
Breckenridge is the place for eating out. There's a huge variety of excellent restaurants in the town (without rip-off French prices) from Cajun to English Chip-shop. Try the Briar Rose or Hearthstone for a treat. Tillie's Saloon serves great bar snacks and has a real Wild West feel to it.