I have done these tours and enjoyed them,
Juneau= Mendenhall Glacier and a hiking tour.
Sitka= Rapter Center and Russian Dancers. I also did a self walking tour which was very easy and included most of the famous sites.
Ketchikan= boat/plane to Misty Fjords and Creek Street on my own.
Personally, I like to book my tours through the cruiseline at about 60 days out.