Did Alaska last year , first week of October.
You will roll the dice with weather . Last year extremely warm / nice .
The following week was rainy /cold.
Did not see Northern lights, I suppose there may be a better chance later in month.
Yes , various shops closed.
Excusions, I would do research to find out which ones would be closed.
We did the Mendenhall hike , (nice weather) thought it was over rated.
Probably look for something else to do next time.
They say the winter season starts Oct 1 so I would be prepared.
Be prepared for the worst , then if things go good it is a bonus.
You do catch a break of ships rates going that late in Oct.