Going to give you my experience on our cruise to Alaska last August. We were on the Royal Caribbean cruise line for 14 days. The route was Vancouver, Ketchikan, Icy Strait Point, Juneau, Skagway, Hubbard Glacier, Seward and then in reverse order.
Back then I was using Nikon D7000 (I've now switched to Canon MK2 with 24-70L, 40mm pancake and 70-200L) and brought with me 3 lenses: Tokina 11-16 2.8, 35mm 1.8 and a 80-200 2.8.
Personally, I would bring the wide and the 200 and that's it. You want to enjoy your trip so travel light. In terms of shooting at 200 or 300, my personal experience is if you don't get the shot at 200, the extra reach at 300 won't make that much of a difference, you are just too far. The 200 is a few stops faster and lighter
. If you are shooting salmon, bring the CPL.
On excursions, I would recommend going on the floater plane in Ketchikan, the views from above is amazing. Whale watching, there will be tons of whales, you can even see them on shores at Icy strait point. If you are planning on climbing on the glacier, my wife and I climbed the Exit glacier. It was fun but the hike was pretty harsh, 2hrs uphill and we weren't even on the ice yet. In Juneau, look for the library in the city, there's a bold eagle nest on top of it, don't worry if you miss it, there's going to be tons of eagles in every city. Lastly, when eating dinner on the cruise ship, always have the tele ready, the dolphins always shows up around dinner time, and yes, I am serious. If you can, bring some sort of rain protection gear for your camera, it rains alot in Alaska.
Hope this helps. Cheers.