Impressive Alaskan resume there Applegater. Makes me jealous.
Our first trip was a bus/train inland the first week and then on a cruise ship the second week. We ended our trip in Vancouver the Sunday before 9/11. We flew out of Canada on 9/9. Had we stayed over like some expressed on the cruise ship we would have been stuck in Canada. It was a good introduction and made our RV trip a bit easier to plan.
I think coming up from Oregon might be easier to extend a stay through September. We have to cross back over the Rocky Mountains at some point and I think that would limit us to the middle of September at the latest unless we swung way south. Glacier NP starts closing up the weekend after Labor Day and is usually complete for all practical purposes by mid-September. We have been caught in freezing weather and snowstorms in Yellowstone and the Wyoming Big Horn Mountains the weekend after Labor Day. The Black Hills was closed up for camping by the end of September.
On the ferry trip did you get off and get on with your B and spend some time in the towns? The ferrys don't plan their trips to get in early and allow you to spend time in the towns all day like the cruise ships. You can't get to Juneau, Sitka and Ketchikan with a B other than a ferry. Skagway and Haines are accessible off the Alaska Highway and Hyder via the Cassiar Highway.