I flew domesticly when I was 12 and 13 and found the gate alright myself. (I am 14 now BTW) At 16 I would think most people can find a gate after check-in by themselves. Unless they are physically/mentally challenged, I don't see why they cannot be told which pier they need to go to and what gate number it is. Tell him to phone you when he gets to his gate so you are sure he is there and you will not be worried.
[This message has been edited by fromYYZ_flyer (edited Nov 30, 2003).]