
I would be cautious about booking anything before we get some snow, especially if I was taking two teenagers.
Cervinia and Zermatt get most of their snow from the south, an area of low pressure forms over the Gulf of Genoa and moist air is transported to the alps. This doesn't happen all that often so you have to be patient, March is the best month to visit Zermatt. Cervinia does better because its on the right side of the main alpine ridge.