Ok, I may be a little chatty here, so please bare with me. I understand your cruise is months away (mine too) but you're still excited. I am too!!!
The last time we did the four day cruise to Nassau and Freeport we did the dolphin swim in Freeport! It was awesome!! The water wasn't as clear where the excursion took place but the activity made up for that small flaw! Living here in Central Florida, we have gone to Discovery Cove and spent almost double what they are asking for the excursion in the Bahamas and Disc. Cove wasn't near as good!
If you do swim with the dolphins, here are a couple tips. As you are going with a group, see how many of them would like to do the same excursion. The more in your group the better (I will tell you why). Also, our excursion was the later one (good tip here also).
If most of the excursion is part of the same group, (I believe 9 was the max for the excursion, we had 8)they tend to do more with you. Also, because ours was the last for their day they took more time with us. My husband, didn't do the excursion and was waiting for me in Lucaya Market Place and he said we were an hour later than we were supposed to be. Even though the water wasn't clear like I would have liked, it was still worth the money, especially if you know what Disc Cove gets for much less interaction. Also, because my husband wasn't going on the excursion, I wanted to spend the morning with him, so the excursion rep was kind enough to give me directions on where to meet them instead of riding the bus from the ship. We were then able to rent scooters and explore the island together before I had to be at the appropriate spot.
I haven't tried dolphin swim at Nassau, but the waters seem to be clearer there, so that could be an option to Freeport if water clarity is a factor. However, if it was me, because of all the other options on Nassau versus Freeport, I would do the excursion in Freeport so you could possibly venture out in Nassau. If you like history and the like you will want to visit the forts etc. in Nassau.
Also, if you like trying local foods (seafood), you must try Arawak Cay. It's not far from the ship, but maybe too far to walk. It's a row of restaurants (actually just before going onto Arawak Cay) and although I haven't tried it yet, I have heard some great reviews from others in our party. (I will be trying it in October though).
If someone wants to venture through the straw market GET THERE EARLY! It is very cramped spaces and you could feel clastrophobic, but you can find some neat trinkets. Plus you could get really good deals if there isn't a lot of tourists around. Make sure you have plenty of small bills and my trick was telling them that's all I had. Haggle Haggle Haggle (I found a hand made photo album to hold our pictures of the trip).
If anyone likes casinos there are more than just the Atlantis, but with a family vacation...
Hope all this helps! Keep us informed and let us know how your trip goes!
Happy Cruising!