We did the Alaska cruise on May 20th of 2007, on NCL Pearl. Whale watching at this time takes lots of patience and an experienced whale watching captain of the boat. We selected the Captain Larry tour and saw several whales, and he has over 25 years experience with tourist whale watching.
Just google Captain Larry Whale watching and visit his site. Be sure to make advance reservations as he is always full. We did the booking directly with his office, and they will drive you via van to his pier. You will also get a great view of Mendanall Glacier as you have to drive past it on the way to Captain Larry's boat.
Our ports of call were the same as yours, and if whale watching be sure to exercise lots of patience.