Jumping in a little late on this thread.
Took my family to Alaska for 2 weeks earlier this summer.
We flew into Anchorage and rented a 30 ft RV for the first week we were there camping in Seward and Denali before boarding the Coral Princess and cruising to Vancouver.
Our ship did visit Hubbard Glacier and Glacier Bay National Park as well as Skagway, Juneau, and Ketchikan.
While I have no doubt that Disney will do a fantastic job with their Alaska trips, I cannot imagine missing Hubbard/Glacier Bay. We love our Disney cruises and will continue cruising Disney, but Alaska is truly a once in a lifetime destination. Different in so many ways from most cruise destinations. To me, Disney's itinerary falls flat. Our Princess cruise didnt have the 24 hour kid entertainment that we get on Disney, but my 7 and 9 year old still loved it.
Finally, if you can do it, the RV portion of the trip was spectacular and my kids loved it. I had never driven an RV before and was a little freaked out about it, but got the hang of it quickly.
If anyone has any questions, feel free to PM.