I want to take a short cruise to Alaska (7 days or less). I am not a party-type person and mostly want to go to relax and view the scenery. I do not like formal dinners and dressing up (although I realize you have to do that at times) and would prefer a line with older passengers and not too many kids/teens. Any suggestions? Also, do you get seasick on cruises and where should you get a cabin to avoid that? I would like a balcony cabin. I am trying to find someone to go with because I understand you get charged the same price for single as for double.
In this case Marc's suggestion of Regent makes some sense
The upfront cost may be high, but it would serve the prerequisites you mention.
If you're looking for a more main stream cruise line, look at Norweigan Cruise Line's Pearl. New, lovely ship, 10 different restaurants onboard, with no assigned dining times, and casual dress (though no shorts in the dining rooms) is the order of the day.
I disagree with avoiding Carnival. I've done Alaska on several lines and the Carnival one was fine. The nice thing about Alaska is that it seems to me that most people choose that itinerary because they want to see Alaska. So, that is where the emphasis is throughout the cruise. I preferred HAL mostly because of the guest lecturer on board....and their bread pudding, but that's another thread entirely!
If you are really interested in the information and lectures, I would again vote for Regent Seven Seas Mariner. Terry Breen is the most informative lecturer I have ever met. Here is a link to information about her book on cruising Alaska.