If you pick a campsite with deep enough water off shore, the child can fish right from camp.  You may come back from a distant paddle to find out HE caught all the fish, right there.  
Does anyone fish with a hook and bobber anymore?  It is a great way to fish, very relaxing and you can let your guard down a bit between casts.  Set the youngster to finding some live bait around camp: worms under damp rocks and logs, crayfish in the crevices along the shoreline, frogs, minnows, put a bit of meat in a piece of cloth or on a line and wait for the leeches and/or crayfish to come to the bait or leave a light on and gather up the bugs as they home in on it.  If there are plenty of fish, I've even had success with bits of old salami as bait.
If the son has an independent streak, then he may soon be leaving you guys in camp and he will be the wandering one.  Teach him how to use the compass and a bit about dead-reconing so he will have the tools to find his way back to you.  If he does have the nerve to get out of sight of camp he will return proud of his new "independence".  (Note: The last 14 yr old I camped with was very careful to never let us out of his sight!!)  :D