Yes, we did the wildlife excursions in each port. Skagway was definitely the most beautiful, we did the "Alaska Nature and Wildlife Expedition" . We took a short catamaran ride to Haines, where there was some nice whale watching along the way, followed by a stop to take some beautiful photos of the ocean and mountains (the best scenery, so beautiful words can't describe) and then we were off to spot eagles, other birds and the like. I just reread the excursion info, if you take this tour in August you will likely get to see bears searching for spawning salmon. I should mention that a lot of people did the scenic railway tour and raved about it, but we didn't have time to fit it in our schedule.
In Juneau we did the whale watching tour - good, but because the whales were just starting to arrive it wasn't as good as I'm sure it was later that summer. Also we did the "Rain Forest Garden Adventure" - we live in Las Vegas so we wanted to take advantage of any chance to spot lots of trees and greenery.
In Ketchikan we did the "Coastal Rain Forest Sanctuary" where we went into the woods and saw spots where bears hybernate (sp) and were fortunate enough to see a momma bear with her two cubs, again, you are especially lucky because of the time you're visiting in Alaska, the bears will be more active, as well it will be prime salmon season.
But in general, we were happiest with exploring the nature, after all, some of the best undisturbed wildlife in the world is there in Alaska. You are so fortunate to be going this summer!