There are countless options. First- did you look over a shore excursion list? Anything of interest? Skagway- is excellent for biking, rent a bike and go out toward Dyea- stop along the way at historic sites, be certain to stop at the Park Service visitor center first for background info.
A just excellent hike is to Upper Dewey Lake, Lower Dewey just about doable for most everyone, trail head between 3-4 across the tracks. Ketchikan, excellent hiking on the Preserverance trail, car necessary but would also give you a look at the area. In town there is Deer Mt. Hiking trail, the top pick is Misty Fjords floatplanes, hiking options available, Southeast Kayaks as mentioned.