L.A.
Our trip to Alaska was almost 20 years ago, and we toured without children. As I recall Skagway is like the "Carmel" of Alaska. Lots of boutique shops in a rustic setting. There was a stream that flowed through town, near the museaum I think, with more salmon than water. We were fascinated and I'm sure your son would be as well. I believe there is a native Indian Village near Juneau. If you're there for an overnight, you might consider renting a car and driving to the North Pole. I think it's about an hour drive and comes complete with a red striped pole and lots of Santa stuff. I can't remember which town we were in that had a sanctuary for injured animals, but you may want to do some research before you go. As far as Victoria goes, Buchart Gardens are lovely with lots of room for your little one to run around.
We toured Alaska in August when the sun stays out until midnight or later. The weather was Bay Area winter weather, some rain and temperatures in the 50's-60's the entire 3 weeks we were there so be prepared with proper clothing and check estimated temperature ranges before you leave. If you have time, consider requesting information from the tourist bureau of Alaska. Princess cruise lines offers lots of nice shore excursions. Perhaps your travel agent can acquire the list before you go so you can do some research on your options before making decisions.
Have fun on your trip. Alaska was memorable for us. We saw wild animals in very unexpected places and it's so different from the lower 48. We took a Princess bus tour for 2 weeks, then 1 week on ship through the inland passage. Our bus driver was a history professor at the University of Alaska and drove tours during the summer months, so every day we got something of a history lesson.