Welcome and gratulations! There are so many incredible places for your beach wedding. Are you set on any specific country or still evaluating. A couple of recommendations would be...
The Rock House in Negril, Jamaica (went here for my honeymoon)
Isla Mujeres, a wonderful little island off the coast of Cancun (I have photographed many weddings here and I got married on the island as well)
Blucacao Beach Club, just south of Playa del Carmen, Mexico. ..:: Blucacao Beach Club ::.. (I've photographed a few weddings here and it's a wonderful and private beach). To give you a feel for the location (and a Mayan ceremony) I'm attaching a slideshow from a wedding I photographed here this past winter. Deneé + Jamie
Good luck on all your planning. You will find a wonderful place that is exactly what you want! I'm sure!