if your in qld the law is: Under 5 meters, Under way and Under 12 year olds. You must be in a life jacket suitable to the waters you are in i.e. pfd1 pfd2 etc. seeing you are over 5 meters he doesnt need to be wearing a life jacket except when crossing bars etc. it would be strongly advisable to have the young tacker in a pfd at all times whilst underway. when fishing it would be too. they fall overboard really quick and its a pain having to pull the pick and go get a drowning kid when the fish are on the bite. Seriously though you cant be too safe with your most precious investment (not your boat, YOUR KIDS).
Rod.
P.S. have a great day Keep a good eye on him