Welcome back, Deborah! I just got off of the Disney Wonder yesterday from our cruise which included a stop in Nassau too! My daughter and I had the most wonderful experience during our dolphins swim at Blue Lagoon. I'm sure you will enjoy every moment of your adventure at Atlantis.
Both the Atlantis dolphin swims and the Blue Lagoon dolphin swims also offer Dolphin Observer options for guests accompanying those doing the swim. The cost is reduced, and those guests get to tag along on the trip, but will simply observe from a separate platform area while you and your daughter are in the water with the dolphins. Afterwards, they will get to spend the rest of the day with you exploring Atlantis or on the Blue Lagoon Beach if you choose that adventure.
Check out these two options:
Blue Lagoon Island Dolphin Observer
Dolphin Cay Observer & Discover Atlantis
If your Atlantis Dolphin Adventure includes the Discover Atlantis portion, be sure to book the observer that includes that. However, if you choose the Atlantis dolphin adventure including Aquaventure waterpark, be sure your observer package is the one that includes that. You'll see them both listed under Port Adventures.
Have an amazing time, Deborah!