Here on Bonaire we have kids sail from 2 years old.
They go on the water with a Starboard Kiddy/Start -board
and 1.5 m sails. They need no experience !! They have to
have no fear of water ofcourse, supervision from a distance
and let them go and have fun. Most of the youngster do not
want instruction, they want to find out how it all
works by themselves.
I started when I was 6, did not take any lessons, just looked at others and have everything under control now.
My suggestion is : Go out on the water with your son and
let him have fun with a board and sail he can handle.
Bonaire, Dutch Carribean