I would suggest these three major sightseeing events as well worth it. While they are costly, you will remember each one for a lifetime.
In Ketchikan, do a floatplane tour of Misty Fjords with a landing on one of the remote lakes. Awesome! You can see a special report on this trip at http://www.AlaskaPortReviews.com
In Juneau, do the Mendenhall glacier helicopter tour with a landing on a glacier. Nancy Norris is currently writing a special report on this trip that should be posted on the same site as above shortly. Excellent tour!
In Skagway, Do the White Pass and Yukon Railway tour.
You can't miss on any of these.
Have a great cruise!