We didn't get Malaria shots, and have made several trips to BZ. My husband, who lives on the island about 6 months a year--and travels to the mainland--was given a pill to take one day a week while he is down there. But he has never taken them. We asked alot of people, tourists and residents, and it does not seem like a necessary thing. But if it will put your mind at ease and help you enjoy your trip, then go ahead and get something.
You'll have a GREAT trip!!