The key to keeping warm in Alaska is layering. It sounds like you're on the right track with your coat and raincoat. Make sure to take some sweaters or sweatshirts, along with a couple long-sleeved T-shirts that you can take off or put on as the weather conditions warranty. If you can find any, I'd also recommend a pair of silk thermals -- I usually have more trouble with my legs getting cold than I do my top, but if you can't locate them, pack some tight or pantyhose to give you an extra layer there.
We did this same itinerary last year, leaving on May 20, and had a great time. Rain in Seattle both coming and going, and rain in Ketchikan. Beautiful weather in Juneau and Skagway, and overcast in Glacier Bay. The only day we needed any sort of "heavy" coat at all was in Glacier Bay, as the temperatures were quite a bit colder there. No surprises with all the ice in the area. I haven't checked to see what the weather has been doing this year in your ports, but I know from another cruise message board that Anchorage (much futher up than you'll be going) had a major snowstorm this week!
We LOVED the Pearl, but we're big fans of NCL's freestyle cruising. No dressing up required, and no assigned dinner times or tablesmates suits our style perfectly. We were in an inside cabin on deck 8, but spent most of our waking hours either on the promenade deck (Deck 7) where they have very comfortable loungers and blankets, or in one of the inside areas where we could watch out.
Have a wonderful cruise!