Blue Lagoon or Atlantis dolphin encounter?

[bfc2406]

As first time visitors to Nassau we are after some advice please about Port Adventures. We had decided initially that we would stay on board the Dream, as we are travelling with a 51/2 month old DS and 6 year old DD and thought that would be best. The thing is, that as the cruise draws closer we can't help but feel we should be experiencing some of Nassau. I personally have always wanted to see inside Atlantis and I know I may be disappointed reading some reviews. Then I read about the Blue Lagoon, with pretty good reviews.
We would love for our daughter to experience the dolphin encounter. Blue Lagoon dolphin encounter or Atlantis dolphin encounter with discover Atlantis? Bearing in mind we have the baby and I would be taking him to watch if possible, what are the best options?
Any advice appreciated! Thank you.