That looks like an amazing cruise! Have you looked at Cruise Critic yet? You can log on to their message board (Roll Call) and talk to other people who might be on your actual cruise, and also see what shore excursions people are planning for different dates, same itinerary, or reviews about the ones they’ve done. We did that with a Royal Caribbean cruise, and ended up meeting many of the group that we’d talked to online, going on group excursions with them. We ended up seeing many of them throughout the cruise, and it was nice to have people we kind of knew, plus they arranged the excursions, and we just jumped on to the ones that sounded appealing. This was all arranged ahead of time.
And if you don’t want to do shore excursions with any of these people, at least there’s plenty of ideas on the Cruise Critic Roll Call that are very specific to your port stops.