Hi Priscilla!
Thank you for visiting the Moms Panel!
There are two car rental locations at Walt Disney World Resort, and these are both operated by National/Alamo, and you would need to contact them direct, to arrange your car rental.
These are:
1) The Car Care Center (near the Magic Kingdom) : Phone: (407) 824-3470
or
2) The Walt Disney World Dolphin Resort : Phone: (407) 934-4930
Both of these operate an efficient shuttle service which will collect you from, and return you to, your Walt Disney World Resort hotel, or a Walt Disney World theme park of your choice.
If you have any further questions, please come back and ask me - I would be happy to help you plan your magical vacation!