I live south of Seattle and have only cruised from there once, but have flown out of Seatac many times. Rule of thumb for Seatac is to arrive at the airport at least two hours before your flight. TSA Precheck, Clear, or other services are absolutely worth paying for, especially with multiple people in your party. Security at Seatac is always long and it's a big airport, so you'll want plenty of time to ride the trams/walk to your gate. If you book an Uber or taxi, it can easily be $75 or more since the airport is about half an hour south of the cruise terminal. Debark asap, hop into a vehicle, and you ought to be fine!