I saw a special on the travel channel about it, it looked like a blast. Can't tell you from first hand experience, though, Alaska is not for me. I can't do the cold. Hopefully, someone with experience will answer you. Have a wonderful cruise!!
We did the helicopter trekking in Juneau and it was great....we would do it again. The dogsled was the other choice, but lots of people told me that it gets cancelled a lot.
As for Alaska, my husband never wanted to go because of the cold weather. He absolutely loved it, and can't stop telling people about how great it was and that was over a year ago. We look forward to going back.
I haven't done that specific tour, but did have an opportunity to dogsled in the Canadian Rockies and I highly recommend the experience. My tour allowed me to drive the sled without a guide on-board (there was one on every other sled in our group). The dogs are amazingly in tune with the driver and they do expect the driver to help them. It was amazing.