Do a combo, train one way and bus the other. Did this a few years ago on my last trip to Alaska. Was one of the best excursions we have had. With the bus, you get to see so much more that you will not see doing just the train-like Emerald Lake. We did not book through the cruise line. We used Chilkoot Charters. Great company. Again, my experience with them was about 5 yrs ago.