Okay, our plans are set, and here's some info for anyone else planning the same type of thing.
The Doubletree Budget at WDW will pick you up at ANY Disney hotel, and drop you off, if you give them 24 hours notice. Also, the Doubletree hotel itself offers shuttle service to the parks. In order to give your 24 hours notice to Budget to pick you up at a Disney hotel to get your rental car, you need to call the direct number to the Doubletree Budget desk, which is: 407-827-8691.
The Code for the Doubletree Budget at WDW is M03. (That is a zero, not the letter 0.)
The Code for Port Canaveral is CC5
We are planning to have Budget pick my husband up at Saratoga Springs, and take him back to pick up the rental car. Then he'll pick the rest of us up at the hotel, and we'll drive to the port, and use Budget's free shuttle service to go to the ship.
We'll do the same for the return.
Each way we'll keep the car less than 24 hours.
My rates, for mid December, mid size car, are:
$43.03 TOTAL for getting to the port
$43.95 TOTAL for returning from port to WDW
Hope this info helps with someone else's planning!