Is he going with a bunch of guys?
There are a lot of fancy "Clothing Optional" resorts in the Bahamas (usually for couples only). There is a topless Pool at Atlantis (Cove's Cain Pool), and the beach is front of the Cove/Reef, allows topless sunbathing as well.
The Bahamas is very clean and a safe place to go.
Having said that, Remember: He is your bf and not a husband.If he wants to go off to the Bahamas with some guys and watch some bare upper fatty tissue bounce around . . so what ?! If you dig in, you will only chase him away and possibly lose him. Let him go and probabilities are, he will miss you very much and will be more loving when he gets home.