Well, being as I was born and grew up in Florida, I can probably help. First, Port Canaveral should be fun to just rent a car and drive around, find a beach, relax. Donít miss Ron Jon's surf shop. It's a cool place; you don't have to be into surfing to enjoy it!
The space center is well worth the trip and much cheaper on your own versus NCL's excursion. Since you have so much time in port you won't have to worry about being late back. Also, check out the Air Force Space and Missile museum, it's free (or used to be) and it's where US space flight was born.
Port Canaveral is obviously the gateway to the Orlando area parks but we're not doing that. If you've never been to Disney or Universal, don't do it in 6 hours (or whatever they give you) I think you'll be disappointed. You need DAYS to see all of that.
I lived in Miami for 16 years. It's a great town to visit, very pretty, but not the easiest place to live. Iím glad to be out of there but anxious to go for the visit. The views entering and leaving the port are spectacular! You don't have as long in this port and I couldn't find easy access to car rentals from this port (I thought that strange) but NCL does offer shuttle service to a couple of different places.
Bayside Marketplace is near the port, on the bay (obviously) and a pretty place to walk around, have a bite to eat, enjoy the views, there is usually a band playing somewhere or other and there are a lot of shops. If Las Tapas is still there, try it. Great food, even better desserts! Try the Tres Leches (three milks) if you like really sweet, gooey desserts.
Some of the canoe tours also sound pretty good, I'd do one of the Biscayne Bay tours as I have done similar trips when I lived there. (We're meeting up with old friends in Miami so we'll leave the tours to everyone else at this port)
Also, I've read a number of reviews that said that South Beach wasn't worth the trip. I disagree, I think you should visit south beach if you've never been there. You are obviously NOT going to find any night life (being the middle of the day, I think this is implied) but speaking as a former resident, during the day on a weekday is the best time to go. Fewer crowds, stroll around, drop into a cafe, and look at the Art Deco. You'll enjoy it.
What's next? Oh yes, Great Stirrup Cay. I've never been there but have been to another "private cruise ship island" and really you just hang out there, you'll have a great time. The waters there are lovely, one of the things that struck me is where you're at anchor and you're getting onto the launch, look down the side of the ship, the water is crystal clear and you'll see the shipís hull curve away and the bottom of the ocean! Itís a unique experience. Depending on where you anchor, you could be looking down 50 to 100 feet and it's like glass!
Nassau is fun. I've been there several times as it's a pretty popular place for south Floridians to quickly get away. (Sort of the like the Jersey Shore for Philadelphians) There aren't too many hours in this port, I'd go to the straw market (always interesting and fun) donít be deterred by the dissenting comments you may read about the straw market. I've read comments like "oh, the ladies are nice until you ask for a price and don't buyĒ First of all, duh! Second, I never really found that, just deal with them on there level, give it right back to them and you'd be surprised at the bargains you'll get!
I havenít been there is years but they used to have carriage rides around the old town. Iíve never done that, planning on doing it on this trip. The queenís staircase is pretty neat, try to count the steps. Thereís a debate over whether there are 62 or 63 (if memory serves)
Well, verbosity is definitely one of my strong traits, so I hope I haven't bored you to death!
You haven't mentioned which sailing you're on...we're on 3/14's.
Enjoy your cruise and let me know if you have any other questions.