[recycled sixtie]

On looking back when our daughter was a teenager we would often take a friend for her to ski with. Once we took a friend whose arm was broken and in a cast before she even started skiing and another time we took a friend who we did not see for a few hours. She was a free spirit, a loner, skiing amongst the trees. On looking back we were lucky nothing happened.

In your situation I would say the father must accompany the son or else not take his son.
You need to have fun and not be worrying about a situation you have very little control over.