I am sure others will chime in and tell you, but you can't leave your personal car in Disney's parking lots. They will have it towed.
But if you don't have a car, you can take the shuttle to the terminal.
You can also leave your car at the terminal for a nominal fee. I forget the per day fee, but someone will post it. My mind goes blank at times (does that come with age - LOL). I have left my car there many times for the 3, 4, & 7 day cruises and forget how much it was.
HELP NEEDED HERE, PLEZ
Then again, it is so convenient to have your car there when you disembark the ship.