To rent or use transportation

[Potbelly]

We are leaving for the Dec.5th. Disney Wonder cruise on the 3rd. My mother, who we will be staying with at the Vistana Resort, is leaving on the 27th of Nov. She says she will not be needing a car while she waits for us to get in. My question is..... should we rent a car at the airport when we get in or have her rent one when she gets in. Keep in mind the only thing we are going to need the car for is getting from the airport to the resort and one day going from the resort to the park and one day form the resort to the ship,or should we bag the idea of a rental car and use ground transportation. IE: Bus,taxi or the such.