Remember if it is a hot sunny day, layers of clothing can be taken off. As well as this, the reflection from the snow gives you a double chance for serious sunburn Sun block factor 15 must be applied to all exposed areas at the beginning of the day and after lunch and don't forget the ears. Use lip salve to guard against the sun, wind and dry cold air. Absolutely essential, even on overcast days. Insist that pupils wear these all day.
Snow blindness is actually sunburn of the eyes and is very painful indeed.
If the main purpose of your trip is skiing, take advice from an experienced skier before your trip as to the correct equipment. Ski hire shops and ski fields themselves now offer excellent ski packages for groups of first timers. If possible, use an instructor for a lesson. It saves days of frustration and gives a definite purpose for your visit. Plan some warm up exercises before the children start.