Absolutely rent the car. Though it's really going to come down to a matter of personal preference when you ask for this opinion, I can say we've done with and without a car at WDW and I will never go back to not having a car. We may not use it terribly often, but it is invaluable for when you need things from the store (which we seem to always do), if you get sick (which I have), if you like to park hop or are dining at a resort hotel. I find driving FAR less stressful than having to put aside an hour of my day just to make sure I get to my ADR in time on the buses.