If your budget can stand it, do a helicopter landing on Mendenhall Glacier. It is a very memorable experience. You can book one off the ship for around $185 or so per person. It isn't often you get to take a hike on a glacier.
In Ketchikan, do a float plane trip to Misty Fjords with a remote lake landing. Again it is very memorable and well worth the money. This will set you back around $175 per person, or so.
Be sure to read the shore excursion reviews at http://www.AlaskaPortReviews.com
. This might help quite a bit.
Have a great cruise.