HI Teacher.
I don't think I would be worrying about malaria on the island. My doctor told my husband (who is spending alot of time in Belize) that he would only recommend the malaria pills if he was going to be in the jungle, and for extended periods of time.
The mosquitos are a whole different story. They have usually been worse north of town, and I was there last May-June.
Just relax, and enjoy.... que sera sera.