So I have 3 recommendations: My favorite island is Aruba as it is out of the hurricane path so you never have to worry about the weather but it is HOT! Great snorkeling off the coast and very low key. You don’t need an all inclusive if you stay near Palm/Eagle Beach as there is a strip of stores and restaurants all walkable. We biked all over the island. My 2nd is Playa del Carmen in Mexico. You can stay on an all inclusive but we actually rented a timeshare and then on a different trip a villa (was cheaper than the all inclusive!). Playa has tons of restaurants and shops and is an easy ferry ride to Cozamel where you can rent scooters or just snorkle. I love Playa best as it’s an easy day trip base for excursion to Mayan ruins.
My 3rd pick would be the Caymans (including little Cayman & Cayman Brac) as the water there is unbelievable and you can do snorkle trips that include trips to the stingray sandbar. If you stay on Seven Mile Beach you can walk among the resorts but it’s not as easy to get around (need to get a taxi to the downtown shopping/restaurants) and when the cruise ships are in port it is packed. But the water is beyond gorgeous!