We ski in Maine and nothing beats the cold like smartwool for the first layer. My daughter is 7, and she likes smartwool because it is soft and not itchy. It can be thrown in the wash, but I usually prefer to dry it on a rack rather than the dryer. I strongly recommend it for the entire family. It has only been available in children's sizes for the past year, so you may not find it in many locations yet.
Great product. My daughter is 7 and on a ski team in Lake Tahoe and loves these pants. (Her others are Patagonia and she likes these more.) No complaints about itchy or coldness. I do however think they run a bit short.