Book a private charter for ANYTHING... (don't limit yourself to JUST whale watching!)
I always tell friends and family, if they want to have a LOT of fun and really get a feel for this area, get out on a small boat, fly in a float plane, and have a drink in the Red Dog Saloon...
Harv & Marv are quite popular this year (mostly due to their amazing tours and being heavily promoted on one of those other cruise related discussion boards!) If you're set on booking them, BOOK NOW... If you they're not available, post back, and I can fire off at least a half-dozen great charters to try.
In Ketchikan, take a tour of Misty Fjords... it's best seen from the air, and there are some great float-plane tours available there.
Happy Alaska Travels!
Better not for now... signatures get me banned!