The complete transcanal is about 6 or 7 hours. However, you can take a 10 day out of Fort Lauderdale on the Island Princess or Coral Princess which takes you through the Gatun Locks and into Gatun Lake. You can then take a shore excursion on a ferry boat through the other 2 locks - very well worth it because you get an entirely different perspective of the locks and it takes you all the way over to the Pacific Ocean.
Both of these ships are called Panamax style because they were specifically built to just fit into the canal. I've done this 10 day trip six times on one or the other. Did the complete transcanal on the old Crown Princess (since turned over to their German branch). There is a new Crown Princess.
The Sun Princess sails around Asia and Australia - not the Canal. The QEII is too big.