Are you porting in Freeport one day and Nassau the next? If so, you could do the Jeep tour in Freeport and then Dolphin tour in Nassau. Just a thought, expensive thought but a thought either way.
Ok, here is my opinion cause I have done the dolphin swim twice. Do the dolphin swim! We are cruisin in Aug. with the Freeport/Nassau agenda and we are scheduling our dolphin swim for Nassau. Yes it will be my third time, 16 yo sons second time, but fiance's FIRST time. His first time or not, I would probably still do dolphin swim. If you do it in Nassau do the Blue lagoon dolphin swim - really great reviews! Yes, you could do it at Atlantis but...Blue Lagoon they say is very nice and you can hang at the beach after the swim. The dolphin swim will cost you about $200 pp but well worth it. There are other dolphin excursions but they are costly too and for the extra bucks; being pushed across the water by a dolphin is well worth it.
We are hoping to do Jeep Excursion in Freeort and Blue Lagoon in Nassua. It concerns me some that when I look at my Excursions to choose from they are not on my list. I called Carnival and they said I have to wait until 90 days out when the more "official" list of cruise excursions are generated. But I am so excited, I want it all booked NOW!!!! Can you tell I can't wait to go.
Good luck and have a great time!