don't forget the mitts/gloves and a warm hat. It's cold in Glacier Bay.
One year we were there the beginning of May and it rained and was cold. Our June trip was perfect weather with some rain. The end of August in Skagway it started out cold and by the afternoon we were "peeling" and ended up were wearing shorts and t-shirts. You just never know what the weather will be like.
You kind of have to take a few things for every type of weather. Make sure you have a good pair of walking shoes. Layering is the best.
Have a grea cruise. I am sure you will love Alaska.