I can't help you on the storage locations, but I have spent quite a bit of time in Alaska.
Sitka is a nice town, I think you'll enjoy it.
Juneau is big, at least big for Alaska.
For all these cities, see if you can plan (if it's not too late) around the cruise ship schedules. Many of these larger ships arrive at the same time in these towns and can easily dump several thousand people into them. Much nicer if you can be there when the cruises are not in town. More relaxed, way less people, and a lot less crowding.
As a kid, we spent a lot of time riding the AMH through South East Alaska. Back then the Cruise ships were smaller and fewer in number. The towns were more authentic, now many of them are centered around the cruise industry and "shopping" trips. I felt that some of the smaller towns have been destroyed by this, but it brings a lot of money in, so a trade off.
You'll get a much more authentic view of Alaska by avoiding the cruise ship vacations. I've been on a few and have grown to hate them. After spending time living in Alaska and seeing a lot of the smaller towns unspoiled by uncontrolled tourism, I don't think I could ever do that again.
Red Dog Saloon is a popular place with tourists in Juneau, but it's nothing like it was, and it's actually moved from it's original location into a nicer building and made to look old. In other words, a tourist trap.
Mendenhall Glacier is well worth the visit if you can get there when there isn't too many tourists. It's quite a walk out to the glacier now, but when I was a kid it was right up near the visitors center.
Shrine of St. Therese in Juneau is a nice place to take a break.
Have a good trip. Expect that it'll rain most of the time. If it's sunny when you are there, enjoy it.