My husband and I are thinking of booking this cruise. We live in Vancouver and this would be my fifth cruise to Alaska.
As for what to do around Vancouver; Stanley Park, Capilano Suspension Bridge, Granville Island, Gastown and possibly Grouse Mountain depending on how much time you have. There is a free shuttle to Capilano Suspension Bridge from downtown Vancouver.
Options for port excursions:
Skagway - White Pass and Yukon Route train
Icy Strait Point - Whale watching
Ketchikan - Self walking tour through Creek Street / Saxman Native Village
Juneau - Mendenhall Glacier / Dog sledding / Mount Roberts tramway / Whale watching
Sitka - Sitka National Historical Park / Fortress of the Bear
I hope that helps.