I've been on this cruise 3 times. I've gone the last 3 years in January out of Baltimore. They've always left us in earlier than the time Carnival states. I like to get there early as a long line forms at the gate before it opens. That way we get on the ship early!
Once you get to Canaveral we have always purchased a shore excursion to Coco beach for a small fee. Coco beach is nice and it is close to the ship. There are lots of shops and places to eat there in walking distance to the beach.
Once in Nassau Bahamas I like to take a cheap taxi to Cabbage beach. It's a nice beach next to the Atlantis resort. Just be aware that there are no restrooms at this beach. We like this beach to sunbathe for a bit and rent jet skis. There is a small snack shack there and of course locals to sell you jewelry and sundresses and adult beverages!
After spending a few hours at Cabbage beach early in the day we head back to the ship to shower and grab a bite to eat and enjoy the ship. Then around 5:30 we take another cheap taxi to Atlantis resort to explore. It's a beautiful place. Once you're there at 6:00 pm the guards leave their posts at the entrance to the very large open air aquarium and the archaeological exhibit called The Dig! So in other words you get in free! We just learned this last year when an employee at the resort told us to wait till 6pm and you're permitted to enter for free. Carnival will not tell you this and will recommend you to purchase a very expensive shore excursion and you must go early in the day and you must abide to their time schedule. I prefer to do it cheap and at my own schedule. ENJOY!! :-)