I suggest you look at Celebrity for a mid-range priced cruise. The dress requirements are never exceeded beyond "country club casual" which imparts a collared shirt and khaki slacks. Their Aqua class dedicated restaurant, BLU, is always casual although blue jeans are not approriate but often ignored. A pricier line, Azamara, is also casual and is doing some Alaska sails this year.
If you are sailing in 2018 you are a little late for the best rates and cabins unless you can get a post final payment deal.
Also, if you are looking at a one way and are not planning on staying landside after the cruise look at Seward or Whittier departures. Anchorage is about 1,500 miles from Vancouver making your trip home much shorter....just a thought.