Possibly a tad on the young side but, so long as you yourselves are competent swimmers and snorklers, you will be fine. Current depends on tides and it varies. Head for exit six and see for yourselves. Having said that, plenty of opportunites for the little chap inside the reef - no need to cross onto the wall side into the current. Loads inside to keep him more than happy at that age. Inside exits five or six should be good. Also, ask for advice at the dive centre. If you do cross over to the wall side, it's easy to guage the current, and it's very gentle a lot of the time. (Sometimes not though!) Just keep a close eye on reference points, and stay close to each other and the wall. If you can get him used to the snorkle and fins in advance, even better. Filitheyo has a swimming pool where you could do this as well, and a sheltered spot next to the dive boat landing stage. Are you considering a bouyancy aid? Highly recommended at that age. (Our youngest was snorkelling in Mexico at 4)