Its not soo bad.. my partner always says she never missed what she never had..
Also there is so many different foods available now from companies like SHS international that you can make pretty muh anything.
Its at this young stage when the mind is developing that the diet is MOST important, when they get older hey will no doubt break their diet, Can only be expected. Also many Teens now are eating as if they did not have PKU, however sooner or later they decide to come back to the diet.
Keep him right as long as you can control his eating habbits, then you can say you have done your part.
You will get on just fine, it may be scary now with all the measuring, and getting used to working out exchanges by reading lables, however it will soon become second nature.