Er… the Valleé Blanche is NOT for beginners!
Chamonix is a first-generation resort developed in the seventies when the French began to wake up to the commercial potential of L’huile Blanche, the “white oil”. Unfortunately the valley runs NE-SW so two of the ski areas (Flegere and Brevent) are south-east facing and get a lot of sun. They are also very steep; the top of the Brevent is unpleasant even for an experienced skier because it’s steep and daytime warming along with heavy traffic means it is often icy.
(The consequences of commercial greed became evident in 1999 when twelve residents of Montroc were killed in a massive avalanche: Montroc avalanche Somehow local developers ignored the warnings of a prominent local guide and local inherited knowledge was ignored and chalets were built in a danger zone.)
Chamonix really isn’t rated as a beginners’ resort, you would do better to go to one of the family-friendly resorts like Risoul or Megeve (nearer to Geneva than Chamonix) or dozens of others, which were built later on north-facing slopes with an easier gradient when the ski industry began to develop the second and third generation resorts. Le Tour does have gentler slopes and faces SW and has nice green runs but not much if you’re going for a week: http://www.chamonix.com/les-domaines-skiables,22,fr.html
On the other hand if you’re a confident skier Argentiere gives access to some of the best piste skiing in the world as well as some of the best off piste and ski tours for later in the season.