I'm going to intrude in your group cruise thread for a couple of posts here. Since you are looking for something to do in Nassau, I hope you won't mind if I try to help a little by sharing some of the things we've done there.
First, the carriage ride, since this has already been mentioned -
We've done the horse drawn carriage ride. The driver we had was very knowledgeable. I asked him lots of questions about their government, taxation, social services, etc. I learned a lot. Seems like it was about $15 pp+tip. Could be more now, as that was about four years ago. The carriages are lined up next to the street after you walk through Festival Place.
Another time, we just hopped a city bus. We lucked out and got one that took a very circuitous route through neighborhoods of the 'real' Nassau, so we saw where people lived and worked and shopped.
The bus driver was a real hoot - taking shortcuts through parking lots and cutting corners to avoid red lights. He would also stop briefly to chat with folks he knew, and give them a ride. One lady got on with a brand new hat. We were pretty sure it was new, because the tag was still hanging on it - like Minnie Pearl!
There is also some good snorkeling there... not great, but good. You can book snorkel excursions at Festival Place, as well. A lot of them go to 'Rainbow Reef.' Very enjoyable ride out and back, and you pass by a lot of interesting places. The smaller snorkel boats (that hold less than 30) are way better than the larger party barge types, IMO.
I've done both, and did NOT enjoy the large one nearly as much as the smaller ones I've used.
Look for an operator with "Seahorse" in the name... can't remember the full name, but they were really good.
If you don't want to snorkel, there's a semi-submersible that's fun and interesting. You actually take a regular boat to where the submersible is waiting, and get a good tour of Nassau Harbor and the shoreline of Paradise Island on the way. DH enjoyed this one, as he is not a snorkeler, but still got to see the underwater life up close and personal.
But, my favorite thing of all in Nassau is the Sting Ray Swim. I've done it two or three times (I forget), and will probably do it again.
This one is a little different than the one in Grand Cayman, as the rays here are captive, and de-barbed. They are in an enclosure that's almost the size of a football field, connected to the beach of an island. The water is shallow at the edge, and graduates to about 15' deep on out.
You can actually SWIM among the rays (if you choose to), rather than just standing around on a sandbar, like in the Caymans. The people there give you 'markers' beyond which you shouldn't go. Beyond that is refuge for any rays who don't want to interact. You can also choose to stay in the shallows. But, those who choose to swim out among them are treated to seeing them glide gracefully through the water, like giant birds, gently flapping their wings, then gliding. If you're lucky, you'll even get to watch on bury him or herself in the sand. Then you'll have a real understanding of why humans are taught the 'stingray shuffle.'
When it comes time to feed the rays, the guides will ask those who want to participate to kneel in the shallow water, in two rows, acing one another. The rays then swim between the two rows of people, collecting their treats from outstretched hands along the way. When the do, some will bump or brush against you, and you'll feel how incredibly soft and velvety they are.
There's a Pirate Museum in Nassau. We would probably NOT do this one again. Parts of it seemed a little 'hokey' to us... contrived, if you will. It might be good if you have kids along. Maybe fourth or fifth grade and younger. But, it just wasn't our cup of tea, so to speak.
CanaryMoon, Thank You, Thank You, Thank You!! What great suggestions you have given to the group. I didn't even know there was a stingray swim thing in Nassau. My middle daughter and I went to Grand Cayman last year. We had a blast. Do you have any information on tour guides on the island? I am sure my girls and I will find something now!!