Yes, in Nassau, either take a taxi to Atlantis or the Marriot or Comfort Suites (just across the street from Atlantis) or take the water taxi if it still stops at the Atlantis. You should be able to find out once on board ship. Ask a member of the cruise staff how they would go over to Paradise Island.
Atlantis in it self is beautiful and a destination that should excite the family. They have a walk through aquarium and dolphin program, which may have an entry fee attached.