There is a place on the beach called windsurf La Herradura.
They have lots of stuff such as kayaks, windsurfers, catamarans, small yachts etc.
For 5 Euros per hour you can rent a kayak and take it for a spin round the bay.
When I was there a group of girls were having windsurfing lessons on a pivot thing on the beach then later we saw them in the sea having their first attempts at windsurfing.
There is a price list in front of the hut and the boss appears to be a Norwegian man who speaks English.
It looks like a good place to take your son.