Can anyone suggest a nice beach wedding venue in the Upper Florida Keys?

My son and his fiancé are looking to get married on the beach in the upper keys. We would have approximately 140 guests. We have a strict budget. A nice beach, a banquet hall that you could bring in your own caterer and alcohol would work for us, or if using the hall’s food, to be reasonably priced. Hiltons and Marriott are just way too expensive. Looking to pay approximately $100.00 pp including state taxes and service fees. Any suggestions?