I have been on the Dawn Princess both north and southbound in Alaska. I have cruised Alaska multiple times. I am also booked both north and southbound on the Dawn Princess May 10 and May 17 sailings.
The Dawn is a very nice ship. It is our favorite class of ship within the Princess fleet. One suggestion on the Dawn Princess is when you are in the fjords looking at the glaciers the majority of people are on the upper decks. Go to the Promenade deck and stand under the lifeboats. You will see just as much and it will be less crowded. You will also be protected if it is raining or misty.
As far as cruising in Alaska goes always keep your eyes open because you never know what wildlife you may see and where you sill see it. If you use a regular camera take much more film than you normally do because you WILL take many more pictures than you think.
Some of the better tours are the Totem parks in Ketchikan. The city tour by water in Ketchikan and kayaking in Ketchikan.
Juneau a whale watch is great here. Flight tours, especially a helicopter ride out onto a glacier is great. Trips to Mendenhall glacier are good here. The Red Dog Saloon is a big attraction in town as well as the Tram up the mountain.
Skagway the White Pass Railway has spectacular views. A trip into the Yukon is good here. Many take flight tours here out onto glaciers also. The town is easy to walk and the Red Onion Saloon is fun here.