Welcome aboard, Angelica!
Both the
Dolphin Shallow Water Interaction with Aquaventure and the
Sea Lion Interaction with Aquaventure are great Port Adventures for the family. I can't really recommend one over the other, as they are pretty similar, the main difference obviously just being that one is with dolphins, while the other is with the sea lions. Both of these adventures allow guests about a half an hour in the water with the sweet sea creatures before heading off to for some wet and wild fun at Aquaventure water park.
Keep in mind that
Blue Lagoon offers dolphin swims and
sea lion encounters as well in Nassau. The price is much less than the Atlantis adventures, and though the Aquaventure isn't included, a nice afternoon at Blue Lagoon Beach does follow your adventure, with various return times from which to choose. My daughter and I will be doing the dolphin swim there because she wants to do more than interact with the dolphins and at Altantis, she wouldn't be old enough for the swim, only the interaction. So, that's something to keep in mind since you have a seven-year old too! We are looking forward to being propelled across the water by one of the dolphins as well as interacting with them!
Let me know if I can help as you continue to plan your cruise adventures, Angelica!