iswym stripeysuit but I don't think you should be allowed to expose your children to huge risks before a certain age. Obviously the definition of huge risk is subjective but surely there is a lower limit at which such an undertaking should not be attempted - if not 13, then would we as a society (obviously in this case it's the Dutch) be happy with a 12 year old doing the same, or a 10 year old? Would we be equally happy if a 13 year old was allowed to fly a plane, or parachute solo?
Personally I'm comfortable with 16 being the defining age for most of such activities. Would be interested to see what others think.