Welcome to cruise-chat!
We were on a Princess land/cruise tour last month. In Juneau we booked an excursion on the ship for the float plane that took us to Taku Glacier Lodge. It was pricey, but worth every penny. To fly over the glaciers, land on the water, visit Taku Lodge (which is a national historic site), etc. was awesome. Plus the grilled salmon, cooked over an open fire, was delicious.
Friends of ours took a helicopter ride to a glacier. I can't remember if that was in Skagway or Juneau. But the helicopter landed on the glacier, they got to walk around on it, and they got some gorgeous pictures. It was their favorite excursion.
You don't have to spend this much money to enjoy these cities. We did because my husband was intrigued with the float planes and wanted to experience it. He loved it!