Even if you have to borrow some, I would HIGHLY recommend that each person traveling with you have their own binoculars. I've been to Alaska twice, and believe me, it is very frustrating when you are whale or bear watching, to try to hand off the bincoculars for someone else in your group to use them. Have a wonderful trip!
I am not an expert on binoculars but would not be without one in Alaska. I have a 8 X30 Carl Zeiss night vision binocular my mother brought back from Germany in 1938. I have used this binocular even since including stunt during Words War II..
Some how about 15-20 years ago I ended up with a pair of Bushnell "Falcon" 7 x 35 at 1000 yards for around$39.95. They have worked fine. I think I may have bought these about ship at the request of my better half
For a pack of cigarettes, while in Russia during WWll got a Russian telescope 30 x 50 from a soldier . I rarely use this because on a ship, a telescope is too hard to use.
Unless you intend to use the item often, I do not think you should spend too much money. While you are on the Inland Water Way, the Lynn Canal or the Glacier Bays or other bays, you really are not far from what you want to view.