We are a married couple and experienced cruisers in our 50's traveling alone on our 12th cruise half of which are on RCL (Platinum level in Crown & Anchor). This cruise was on the Adventure of the Seas for the Southern Caribbean itinerary from San Juan to Aruba, Curacao, St. Maarten, and St. Thomas. This was the best cruise vacation we ever had. Why? The itinerary, aft balcony room, the ship dining (food & service), and no children (of ours anyway and the others stayed mostly out of sight).
We had three cruise goals that were all met: relaxation (the less stress, crowds, and schedules the better); great snorkeling (we got it at Curacao and to some extent at Aruba); and plenty of alone couple time (the balcony and comfy bed fit the bill). So I can't give much advice on most of the ship board activities or shore excursions. We took only one of the latter and limited the ship activities to choice entertainment in the large show theatre or Crown & Anchor or Cruise Critic member events.
This is a Voyager class ship and the first of that class ship for us. Personally, this is too big a ship for me. If it had not been for the balcony room, I probably would have been an unhappy cruiser. We are both active, but we did not take advantage of the remarkable activities on board that this class of ship has rock climbing, skating (ice & in-line), miniature golf. But they all looked great from the cruise video, much used by children and their parents, and would make this a really fantastic cruise to take for school age children and up.