There are a few dolphin interactive parks, you will find most of these in places like Bahamas, Mexico, Anguilla, Tortola and possibly the Cayman Islands. Funnily enough these are also very popular destinations with the US market, so there may be a reason there.
You won't find interactive parks in Barbados, Antigua or St Lucia for instance, but you can go on boat trips to see marine life, up close and real, but you will see turtles or stingrays instead. Keep off the reefs, swim over them, do not touch them, they die.
I don't like these parks myself, so if you do decide go to a park to swim with dolphins, do it somewhere there is a medical and research facility/institute/university affiliated with the swim with the dolphin program. This way you know you are giving your money to a program that takes care of their animals.
Dolphins and other marine mammals have been displayed in captivity for over a hundred years for the purposes of human entertainment, research and, more recently, for direct physical interactions such as "swim-with-dolphins" programs. While those who have experienced it might say that touching, feeding or swimming with a dolphin is one of the most captivating experiences of their lives, others, including environmental groups such as the UK-based Whale and Dolphin Conservation Society (WDCS), have expressed grave concerns, supported by scientific studies, about the health of marine mammals in captive facilities.
Most of the Caribbean is about lazing around. If you DH has any interest in excursions to waterfalls, rain forests, snorkeling and swimming, kayaks and hobie cats sailing, I'm sure he'll enjoy it. Many hotels do not offer motorised watersports anymore due to the insurance and maintenance costs. You still get jet skis and other power boat fun and games but normally these are payed for locally and are privately run by the beach operators.
There are many operators offer Almond Beach resorts and there are 2 Almond Resorts in St Lucia. Rex resorts have hotels throughout the Caribbean and offer good value, slightly more basic (more Caribbean) and in my opinion are on lovely beaches, the one is St Lucia is in a great location if you are not on all inc as it is near Rodney Bay village with many bars and restaurants. There are some really nice hotels in Grenada too.