We cruise a lot on various lines. I would stay away from NCL for Alaska...they haven't been doing it long and they get the worst port areas. In Ketchikan they've built a port away from the town so you can't just walk off the ship and see things which is a pain. Also they've cut down the entertainment options which used to be wonderful and they've cut their service staff so rooms and restaurants do not have enough staff to give good service. I'm annoyed about this because I often cruise solo and NCL is the best for that market.
We did a Princess Norway cruise in June and it was wonderful. Excellent service and beautiful ship. We were busy each day and night with many choices of activities. Princess is known for giving the best Alaska experience.
Holland America we did once to Alaska, I wouldn't recommend. It was an older ship and it wasn't kept up.
Carnival which I really like for certain reasons only sends old ships to Alaska, and they aren't well kept up. No go.
We've done Alaska on
DCL, it was ok, wouldn't choose it again.
RC is fun but I don't find the activities as enjoyable as Princess.
Cunard, just did a TA with them and loved it, am seriously looking at them for our next Alaska cruise.
BTW, you don't need a balcony for the cruise. We've had everything from insides to two bedroom suites and tbh we just don't use a balcony that much. You have a much better view from the open decks. Do your research and choose based on itinerary and ship. If you drink at all get the drink package, you'll save money. Excursions are expensiveI in Alaska so to be safe I'd budget $1500 for the two of you. That isn't going to get you helicopters to the glaciers or the other pricey ones but it will allow you to do something fun in each port.