The excursions you book on the ship are very expensive, but they are worth every penny. I recommend the Misty Fiords and the Yucon Territory. There may be a chance to buy the trips at Ketchican and Skagway. I was told so but I am not quite sure. They should be cheaper.
Always remember that if you go it alone you are responsible to return to the ship before it sails Not the place to be left behind.We quite often go it alone but in Alaska we doid the tour.