Not sure about the consistancy at that time, but the north side of the island is def the place to surf. Ive been there, in fact my profile pic is from Encuentro. It does get heavy but there is an inside break where you will always see little european kids w/ reef booties on, learning how to surf. Get on it early, as the winds do too. The trades pick up consistently everyday around 8:30-9 and everyone trades their surfboards for kiteboards. If you want to surf ALL day.... head to Nicaragua, offshore most of the time. Cabarete is the coolest little party town I have been to in a while. A guide is not a bad idea if you get sketched-out easily. Everyone will hassle you for extra tips and money if you stand out like a tourist. But, all in all good vibes, great food, beautiful scenery, and tons of fun stuff to do and see. Good luck!
Encuentro is the most consistent break on the north coast. And the most crowded. Turistas & locals flock here when it's firing. Although it's listed as a reef, it's shifty & many times it has more of a beach break feel. The Point at Encuentro, in front of the little shack restaurant on the beach, is where the locals like to sit. Encuentro can get territorial, as very good local surfers will not hesitate to hoot you off waves. Snaking isn't uncommon. The guys are pleasant & friendly, just stay out of their way; they will aggressively lay claim to waves. By the same token they will help you out if you get into trouble in the water.
Sometimes Encuentro gets big, most days it's smaller & thus has something for everyone. There are several surf schools that teach novices on the inside at Encuentro.
You should go out early in the day at Encuentro. Reason being, the sideshore wind comes up at 1030-1100 every day, like clockwork, and it cranks. That's the end of the waves. That's when the kitesurfers come out & take over up the road in Cabarete Bay.
You may want to bring a pair of surf shoes. The urchins are no joke here. The locals all surf barefoot. You're only there a few days with not much time to toughen those feet up. The urchins are huge. Bring some tweezers & Neosporin, just in case.
The paddle out is the channel just to the side of the shacks on the beach. Sometimes you can get a good current going out. Water depth is 10-20' for the most part.
Coco Pipe is next to Encuentro. It is not realistic for your son. There is razor sharp coral & large urchins & rocks 3 feet under the surface. Because of that shallow depth, it can get big but only on the right swell. It is only for expert surfers.
Sosua Bay takes a certain direction to break & is usually not worth the 20 minute drive.
Playa Grande is a beach break, sand bottom, approx one hour drive from Cabarete. There is another break named Preciosa, which can get big, around the corner from Playa Grande that you scrabble down a steep jungle hill to access. Both these breaks need a certain swell to work. Your guide will know about this.
Board rentals: if you rent, be aware that if you ding the board or break it, you will be expected to pay from usd 100-600, cash only, on the spot. Beware of repaired/patched-together boards & worn out velcro on rental leashes.
Size at Encuentro totally depends on the swell. It can get huge, but that time of year usually not huge.
Lots of petty theft in the DR. Keep your stuff tight. Make 2 copies of your passport & keep separate from your passport. If you don't need a laptop while there, don't take it on the trip. People are very friendly. Great place, fun times.
Getting up early to surf has its advantages. Namely, you can spend the afternoon chilling in the beach restaurants in Cabarete. LAX restaurant in Cabarete is a cool place to chill with icy cold Presidente cervezas.
BTW, very cool place to stay, wonderful people, reasonable rates, clean & quiet, very secure & gorgeous condos literally on the oceanfront in Cabarete is the Hotel Magnifico. www.hotelmagnifico.com
A great place to surf for you & your son is Barbados. Being an island, it has breaks of every level of ability.
Highly recommended local guide: Melanie Pitcher of Surf Barbados. And yes, she can surf, ex-pro on the tour. However, she's real cool & low-key & knows every single break on the island. She can find something that's perfect for your son & for you, every day.
Barbados is more expensive than the DR, but, in life you get what you pay for.