I am not quite sure where we are "at" but it is becoming law in Austria for children up to 15 (?) to wear ski helmets for safety reasons.
See
http://tirol.orf.at/stories/408832/Such laws will need to be passed in each Bundesland and it looks imminent.
It's a good idea anyway. I have sat waiting in hosital casualty with someone who had an accident and the statistics on the wall about the huge number of ski accidents was absolutely frightening.
Don't get caught out. Make sure your family are protected anyway.