For starters divide them in 2 groupsj and play races to see wich group wins, do that in boots, with one ski, and boath, that will get you throu an hour, at least. They can allso play tag, and whenever one is it, he has to swigh his ski...
than procede slowly to stoping, and while your on the bunny slope use cones or ski poles to mark the places to turn, or set them up a course where they have to duck, jump over, turn around poles and stuff... dont bother them with poles for the first 2 days
good luck