i dont know anything about the beach, but when we did the aquarium it took a little over an hour to do the tour which actually move quickly, it si a huge aquarium, well worth seeing.
Gambling is 1 minute walk across the lobby in the hotel from the aquarum entrance so they are close together and easy to do.
A taxi takes about 10 minutes to get there from the port in the morning, the afternoon is heavy traffic and I would allow 30 minutes to be safe to get back to the ship. There is also a water taxi which takes about 15 minutes, but not sure what it costs.
Hope this helps some,