We were some of the lucky people that had the great weather in Juneau last week and flew with Temsco up to Mendenhall glacier to do some dog sleding. Talk about the experience of a lifetime! It was the absolute best! but we did have a back up just in case the weather was bad, which from what we were told is quite often. We did not do any whale watching but the people we knew that did came back with pictures that could rival the discovery channel. Not only that a great deal of whale watching tours in Juneau offer a refund if you dont see any whales. Great deal with you ask me.
Another great excursion we took was the Safari Wilderness tour in Skagway. Everything from hiking to canoing up to a glacier to picking wild strawberries to skipping stones in the water on the beach. Another great experience! But everyone is right, ALWAYS have a back up. Mother nature is a temperamental woman.
Ketchekan it rains 95% of the time so we took a horse drawn trolly ride and were very pleased with it. Even got to see some seals in the harbor and lots of salmon in the ladders.
Hope this helps a bit and Good Luck!