In answer to your questions,
1. The first formal night was the second night of the cruise. The first night of the cruise was actually really strange for dinner. There was open seating in the dining room and frankly it was kind of a mess. The waiters were unmotivated, and no one seemed to know which table belonged to them. For the first night, I would strongly suggest the buffet. After the first night, when they switched back to the regular format of arranged seating and assigned staff, it was wonderful.
2. Which way are you going? From Anchorage to Seattle or Vice versa? We did Anchorage (whittier) to Seattle, and we had stayed previous days in Fairbanks & Denali, so it seemed to us even in Anchorage (whittier) to get dark fairly early (after at 2am it being "dusk" in Denali). The curtains in the room though are very light blocking, we never felt that we needed more light blocking than we had. If you have an inside cabin, it's not an issue at all. All in all, I'd say no on the eye protection.
I put some postings about the excursions we took in the "Ports of Call" section if you are interested. Hope you have an awesome cruise!