As far as transportation from Sea-Tac, I'm not sure how much luggage you will have, but there is a light rail link between the airport and Downtown Seattle. It's with Sound Transit
. The maximum fare is $2.50 per person. Once you hit Seattle, the light rail goes through the Downtown Seattle Transit Tunnel, so then you have the hassle of going back up to street level, and getting a taxi to your hotel. The Downtown Seattle tunnel is underground, running underneath Third Ave.
In a taxi, the ride from Sea-Tac Airport to Downtown Seattle is about 20-30 minutes depending on traffic. This is why taxi fares are high.