Your best bet is to go through all the excursions offered by the cruiseline and try to pick some of interest. Good idea to whale watch in Juneau. Also, another good one is the White Pass railroad, it is on the long side but very scenic and interesting bits of history of that area. Many more to choose from, taking a helicopter ride to a glacier, fishing, etc. Just beware, almost all of them are pricey, so pick and choose wisely.