You'd still see snow in many places - depending on the weather that year. To me, Hubbard is jaw-dropping - when you can get in to see it. Glacier Bay is cool, lots of wildlife. But that early, there will likely be a lot of ice in the water so the ships won't get as close.
In Skagway, I would recommend Chilkoot Tours for the Yukon rail & bus tour. It's pretty cool!
Ketchikan is a great place to buy inexpensive rain jackets - and you may need them. There are several places by the pier. We usually ended up at the Tongass Trading Company. It's especially great if it's your first stop