You'll have a great time. Princess is very similar to Royal Caribbean, so I'm sure you'll enjoy the shipboard experience.
Alaska is an amazing destination. Alaska is a huge state, so I'm glad you're doing a 5-day pre-cruise tour in Denali. The distances are large and it's much less frenetic to spread out those trips over a few days.
There is so much to see and do at the stops your ship will be making. If you look at the selection of excursions, it covers every interest, every time span, etc., you could want.
The weather should be cool that time of year, so make sure you pack clothes you can layer to stay warm. The coldest days will be the days you sail close to the glaciers. You'll want to be outside, with binoculars, on those days, so bring appropriate clothing.