There is a good chance that at this age, they will not really 'enjoy' the skiing itself - best stick to the fun aspects of playing in the snow. If they take to it, they can have fun on skis, zooming around your resort's 'snow garden' and learning to ski in the process, and I wouldn't want to put you off taking that route. Our solution is the compromise - a bit of both. Once the child has found his skiing feet the theory would be that it really is time to hand him over to the professionals in the ski school. Less obvious, but equally important, are the arrangements for getting the children to and from classes.
Tour operators can be very helpful here.
So now the child can join in your explorations of the Trois Vall es. Great fun, no doubt.