I did not go through the canal. I went on the Grand Tour we went to the Gatun Locks and watched a ship pass, then on a boat in the Gatun lake to meet the Umbria Indians which was a very nice tour. Post this question on www.cruisemates.com
message board under shore excursions and Im sure it will be answered. I do know people enjoyed the tour your talking about. Pack a rain poncho and you will be fine if it does rain.