HI; here is a quick breakdown of the Seattle area. From SeTac Airport to the Seattle Pier is about 25 minutes by Taxi (30.00) or shuttle 12-15.00. From Seattle to Vancouver is about a 3 1/2 hour drive; but you can do a train that leaves each morning if you can work your flight to be here by then.
If I were you I would leave from Seattle to Alaska and you would have to come in the night before your cruise because of time change and flights. Seattle is a very safe and fun city with lots of reasonable hotels, plus you can walk to the Pier from just about any hotel or take a 5.00 taxi to the Pier.
If you give me more info on where you are from I can help you out a bit more. I am originally from Boston and now live in the Seattle area.
Let me know if I can do anything further