I respond because we took an Alaska cruise leaving Vancouver on May 4. That corresponds pretty well with the date of your planned cruise. We had very nice weather. The coldest I remember was the cruise through Glacier Bay. Otherwise we just wore light jackets for the most part. We took the train ride up White Pass from Skagway. I would certainly recommend that.
Click to see train ride
The date of your cruise means that you may very well be the first ship into some (maybe all) of the ports. We had quite a welcome in Juneau with native dancers, bagpipers, bands, the works. It made us feel quite special.
Click to see our welcome