You have two options with a vehicle...
- drive onto the cruise ship level and your blend in with the taxi's unloading the heavy stuff straight to port staff. Passengers can then walk over to the security lines for boarding. Warning.... traffic into the boarding area is VERY heavy between 11:30am and 1pm. I like to arrive before 11am. No need to pay for parking with this option.
- drive straight into parking below the cruise terminal. Take the luggage up the elevator to the cruise ship level and hand the luggage to them there. Not sure if you are allowed to leave your vehicle there for a week, but a great option if sister is just seeing you off.
To clarify, where is this Seattle vehicle going to be parked during the week long cruise? Airport? Hotel Park 'n fly?