With that many people, why don't you pick a few places in different price ranges and let your guests decide for themselves where to stay? I would recommend working with a travel agent. Pick out a few and provide the info to your guests along with the travel agent's name and number, and let the travel agent know which ones you chose. Your guests can then contact the agent and go with the hotel that best suits their needs. What hotel will the bride and groom be staying at? I recommend that they choose a few hotels they would like to stay at and then contact the hotel to see what they offer for wedding packages.

I too will be married on Ambergris Caye this April. Hope everything goes well with the planning!