On way north, I would go to St. Helens volcanic center and even to the mountain.
I am guessing that you will be taking BC ferry to Vancouver, BC. Black Ball Ferry into Victoria is nice trip across Strait. While in Victoria make sure plan time to go to Buchart Gardens. It is outside of Victoria.
North out of Vancouver, BC is Hell's Gate. Interesting location where the Frazer River goes through a tight channel with suspension bridge across it.
Make sure you take your time to Alaska. Many things to see along the Alaska Highway!
