We really enjoyed the whale watching in Juneau, we went with Capt. Larry and were able to pre-book, but it was really interesting and a nice excursion.
Do you have a Glacier stop, those are the best...we had an absolute beautiful day and could hear and see plenty, what a sight, hope you get a stop like that during your cruise. We also did the White Pass Railroad in Skagway, its rather long, but very informative on the way up, just beautiful country, worth seeing.
Hopefully Karen16 can add to this, she's the local "Alaska" specialists and can give you many more tips, etc....
Katen....where are U?