So difficult to advise anybody without knowing more about your level, style, etc. Haute Nendaz has always been one of our favourites. You can choose your pass to suit your ability- the local pass is great for beginners and good intermediates, or you can take the 4 Valleys pass which will include Super-Nendaz, Veysonnaz, Thyon 2000 and Verbier- then take a 1 or 2 day supplement to go to the Mont Fort Glacier for the bumps if you are up to it.
Please do not attempt Tortin/the Wall unless you are excellent skiers. So many try it just to say they've done it- and injur themsleves seriously. NOT worth it. The childrens'/beginners area at the top of the main bubble up from Nendaz is great, with a travellator, and a great ski school'kindergarten for little ones, with a restaurant right there, so perfect if one or two parents have to keep warm with little ones, whilst others go for a ski. Look at
www.interhome.ch perhaps to find a chalet/appartment. Or perhaps the Hotel Mont d'Or (ex Le Sourire) - and make sure you have an adult meal at the Mont Rouge, the best restau there.
BTW it won't apply to you as the kids are so young, but all the resorts in the 4 Valleys, including Verbier, have great offers for families. We only ever paid for 2 adult passes for a family of four- 1 parent pays full price, the other 50% and the kids 25%- this can really make the difference between skiing in a French resort or in the 4 Valleys.
Champery's skiing is up in the bowl above, called Les Crozets. It's a great ski area. It links with the French resort of Avoriaz - again do not attempt the Wall returning from the French side unless you know what you are doing. Same as above. The resort also links with the smaller resort of Champoussin and then with Morgins and Chatel/Chappelle d'abondance and Torgon- all in the Portes du Soleil area.
And for a rest there is a nice spa in Val d'Illiez a bit below.