Hi Ashley, welcome aboard! It's funny that you ask this because my family will be sailing in November on the Wonder's Bahamian cruise as well and we'll be surprising our seven year old daughter with a dolphin swim in Nassau too!
I've chatted with lots of folks about the different options for dolphin adventures in Nassau and have received almost unanimous votes for the
Blue Lagoon Island Dolphin Swim. Atlantis' version of the "swim" is for ages 10 and up, so that is automatically out for a seven year old.
The "encounters" in shallow water with the dolphins are quick and I hear that the trainers move people through their five minute personal time with the dolphin very quickly at Atlantis. At Blue Lagoon, the same can be said for the Dolphin Encounter, as it's a quicker, less involved interaction with the dolphins.
However, I hear only rave reviews for the Dolphin Swim at Blue Lagoon. Our seven year olds are just old enough to participate, and will get more time with the dolphins. I'm thrilled that not only will my daughter and I get to interact with the dolphin one on one, but also each get to experience the "push" across the water as the dolphin dives under our feet and propels us across the tank. I cannot wait and I'm sure my daughter will be thrilled as she is a big dolphin lover! For both the Blue Lagoon and Atlantis trips, you'll see the dolphin observer options for the rest of your family to come along and watch you.
Of course, if you are dying to see Atlantis, doing one of the dolphin encounter combo adventures will allow for this, but you'll be staying at a much nicer resort in my opinion: the Disney Cruise Line! I'd take that over the Atlantis resort any day!
Let me know if I can help with anything else as you continue to plan! Perhaps we'll be on the same cruise this fall!