Hello aberg,
As a wedding planner in the Riviera Maya, and living in playa del carmen, I do know that the prices in February fall into high season and the weather is simply perfect. you will not be hit by spring breakers at that time. On the other had if you hit april again you will get the warmth but it is really bearable especially once the sunset.
A little note, The Royal Playa del carmen inside town that means the beach is very busy, lots of tourist taking their walks there. Which makes your ceremony and reception semi private.
I would check with the Travel Agent from the BDW and they can advice on the exact price difference.