Thank you all for your help. We had a nice cruise and we did fine at the ports of call. The input from fellow posters helped a lot in making it a fun experience.
Here is what we did at 3 ports:
1. Port Canavera: Did nothing...stayed on the ship as was planned. I just walked out of the ship to see options to go to Cocoa Beach. They are offered at $5 each way per person.
2. Nassau: All of us did the "Seaworld Explorer" excursion from Carnival. It was a good experience and we got to see marine life on the ocean floor at 3 different reefs in a decent Submarine boat. Spent about $176 for 2 adults and 2 kids. There is a 5 minute walk from the ship (the tour greeter meets you at the exit of the ship at 12:15 PM) to the boat that takes on a nice 15-20 minute ride to a place where Submarine is located. On the way, you get a nice commentary bu the guide (ours was very funny too) to the paradise island buildings and such. Total submarine time must be around 3--45 minutes but I didn't time it. The excursion ended at around 2:15 PM. We went straight to the straw Market shops (right across from the pier) and spent about 20-30 minutes for souvenir shopping. Very crowded place and bargaining is the way to go. After that we walked back into the ship for some food and cam back out around 4 PM. Took a taxi to Atlantis resort for $15 for 4 people. There are ferries to the paradise island too ($3 per person each way) but I was told that there is a bit of walking involved with this option if you are going to the Atlantis. Also, the last ferry back is at 6 PM. In our taxi, there was no one else and due to a bit of bargaining, I was able to get it for $15 total for 4 people with no toll charges to us. The Atlantis is awesome and we were able to see a good portion of the Acquarium (but don't know what we missed) and walk around the propoerty with some restrictions, go to casino etc. I found this to be enough with no money paid to Carnival or Atlantis. The return trip back at around 7:30 PM was easy with $4 per person rate and sharing the taxi with others.
3. Freeport: We docked at around 7 AM but got out only at around 8:45 AM after family finished the breakfast at easy pace. The taxis there are easy to get and regulated at $5 per person for a ride to Lucaya beach. The ride is about 15-20 minutes but it is worth it. The shops at Lucays beach are "LOT" better than the crowded Straw Market in Nassau. The beach was awesome with clear waters and fine white sand. The only fee we paid was for the beach chair rental at $5 each. I did the Jet Ski rental with the kids. We got it through an agent on the beach. She sold it to me for $60 for 30 minute rental. The Jet Ski had 3 people space and for the first 15 minutes, I had both my sons with me (5 year old was in front of me and 10 year old behind me). I was the only one with shades and hence the little one in front requested to be dropped off after some time as salt water was burning his eyes. We used the Jet Ski for about 40 minutes or so and they never called us back. I just returned since I felt we did it for long enough time. This was very exhilirating experience. They have two rescue boats operating in the area and I felt safe at all times (otherwise i wouldn't risk my kids' lives). The beach time was awesome and provided for some excellent photo opportunities. After some more shopping, we got a taxi back (started at 12:15 PM) to the ship.
Please note that there is no check by anyone if you take the food out of the ship in Nassau or Freeport. Port canaveral is a different story though. They have strict policy and check for this.
Not knowing this before, we didn't take anything out for Nassau and Freeport.
All in all, very satisfied with how we used our time and port selections.
Hope this helps.