Hi! My husband and I have been to Nassau twice, and love it. It is a little dirty compared to some of the other ports, but the beaches are beautiful and it is unique. If you do not mind a little walking, we enjoyed Ardastra Gardens and Port Charlotte (we could have taken a taxi, but we visited it on our first cruise and decided the walk might be good for us considering how much we had been eating, haha). We also enjoyed downtown Nassau shopping and sightseeing and ate at Hard Rock (kind of expensive for a Hard Rock, but we ate here on both trips since we were unsure of other restaurants). Cable Beach is beautiful as is Paradise over at Atlantis. We opted to book our excursions at Atlantis directly through them instead of the cruise line and did save some money, but it depends on the excursion.
Hope you enjoy your trip!