Have you done Treadwell Mine in Juneau? The kids and I go everytime we are there. It's easy to get to by public bus, or a quick cab ride over the bridge to the opposite side of town. It has some nice walking trails and things to see, as well as a beach and stunning views of the ships from the opposite side of the island!
Treadwell Mine Historic Trail | Juneau Walking Tour | ALASKA.ORG