you dont need a car at all...
**this is just my opinion**
you are PAYING for disney to transport you , lets face it, Disney isnt ur average trip to the beach, it gets costly so adding on the cost of a rental car isnt nesessary...... yes sometimes (like at park closing) you may have to wait for a 2nd or 3rd bus, but generally they are pretty speedy. and plus, at the end of a loooooooooooooooooonnggg day of walking ,...why would u want to have to get in the car and drive all the way back yourself when someone will do it for you?!!
--------->>>>>> when we stay at All Star Music we bring laundry detergent with us..you can either buy those little "to go" boxes at home or simply put it i small containers(like little dollar store bottles) and make sure to put those bottles in a sealed ziplock baggie and ur good to go!!!
~~~~~>>> with the food question, garden grocer will deliver to you . just go online and order and it will be waiting at the resort for you...MAJOR help!! who wants to waste valuable Disney time at the grocery store?!

or you can go on costco.com, we always do that and send a case of water down so we dont have to pay. i know you can order water from staples as well..
**just a couple suggestions ..hope they helped..good luck and HAVE A MAGICAL TIME!!!**
