thank goodness your son in ok and congratulations on his new helmet. Just make sure he always always wears it. As for your other making fun of your worries, calling you over protective, try a dramatic presentation. Take an egg, hold it in the air, and say this is your brain in your head without a helmet. Drop the egg and as you clean up the mess say "and this is your brain in and out of your head, on the ground without a helmet.

Best example I have is the cracked and shattered helmet from a fall (broken ribs, collapsed lung, road rash but no concussion) which I keep around to show people why they need a helmet.

marni