If you go to cruisecritic and sign up for the Roll Call for this exact cruise, you'll 'meet' people you will be cruising with. Good chance there will be 'sail-away party, possibly a Cruise Critic Meet-n-greet (sponsored by the cruise line- they LIKE Cruise Critic) and there is an excellent probability that some of your fellow cruisers have set up private tours to various sites. Often at half the price the cruise line charges. Don't worry about the 'miss the boat' tactic. I won't say no one has ever stood on the quay and watched the ship disappear over the horizon, but those tour operators are the very same ones that the cruise line uses and they pick up cruisers and have them back to the ship before sailing time EVERY TIME a ship visits their port. Probably daily. The last thing they want is a bus load of pissed off tourists plastering their name all over TripAdvisor about stranding them on the dock. It simply isn't going to happen.
Now go sign up for your cruise's Roll Call. It's fun!
Jim