I am also currently looking it to this for our 4 year old who i want to have lessons and my 11 month old. I have done it twice before with one child but taken the mother in law both times and she looks after the little one while we ski. Then we meet her for lunch and then at the pub for happy hour afterwards.
First time we went to Morzine as I knew from the biking holidays I could hire a decent place, get there on easyjet and transfer cheaply and quickly. This worked well for the MIL as she could wander round during the day and there was plently to do.
Second time we went to les Arcs 1950, great resort for the skiing, but MIL have to use a sledge to transport the little one, and much less for her to do during the day. The transfer was not nice either.
So for this year, I am unsure and looking on here for ideas.