You already know cozumel and should try now Playa del Carmen. June is getting to the end of the wind season you are right but we actually have a very good end of season so far with a lot of steady wind and perfect weather.
A perfect family spot would be to stay at the Sandos Playacar Resort, in Playa del carmen itself!PDC Kiteboarding School
is located right on the beach in front of the resort!http://pdckiteboarding.blogspot.com/
From there you have about a mile long of private uncrowded white sandy beach to ride. The resort offers everything you need for kids and no-riders!
In case of no wind, you can Scuba dive, snorkeling, sailing, wave running, parasailing......etc.
5 min away from there is the world famous "Quinta avenida", the busiest pedestrian avenue in Mexico where you ll find restaurants, shops, beach club, and a lot of night life!