Having worked and skiied in a number of resorts in France the one that comes out tops for children is Valmorel. Although purpose built, it is a very pretty resort, with an authentic village atmosphere. The place is 'walkable' and they have a number of street parades in the evenings and lots of activities for children. They have the "LES PIOU-PIOU" childrens club which offers ski lessons, acitivites and childcare, among other things. When I was there for a season everyone had a long breifing from the team in charge of children's activites and they really do place a lot of importance on what they offer. Its a very special place with an almost magical atomsphere that is great for kids and plenty to offer to adults too. Skiing is good (large area) and challenging if you want it to be. Valmorel would be the 4th valley from Val Thorens if a link was made.