Unless you are traveling the day before/after a cruise is set to leave (usually a Thursday/Friday/Saturday), there are so many flights that it is generally possible to get on something. As with most flights, Tues/Wed is generally the best. If you decide to head up to Anchorage, PM me and I'll check the loads for the dates you want.
As to activities, there are so many in Alaska. Teenagers, however, don't seem to appreciate the villages the way adults do. There isn't much to do that isn't hiking and fishing in the small communities. Anchorage, however, has a multitude of options and a city (small though it is) that teenagers seem to appreciate. They just can't seem to live without their phones <g>
Never been to Montana. It's on my list for next summer so let us know if you go there.
Bookmarks