we always rent a car now (when we stay at the BWV, we rent at the dolphin alamo/national - they are wonderful there!). we don't use it to drive to the parks though, we find WDW transportation faster than going to your car, waiting for the A/C to cool it off, driving to the park, waiting on line to get a spot, parking, getting a tram, and
finally entering the park

we use the car to get groceries, eat offsite, go to the outlets and DTD (we prefer the short drive, no waiting and no trams there), etc
just a suggestion.: if you rent at the airport, you can opt for a smaller car if some of your pary takes magical express, and all your luggage goes with them.
or you could rent at alamo/national at the dolphin or car care center, dollar across the street from SSR, or one of the other places near there. then you would not only have the option of renting a smaller car (since one adult can get the groceries while the other watches the kids - they can enjoy the resort or take WDW transportation to a park, where you can meet up with them later, if you would like), you could also rent for fewer days. that can be a big money saver, especially if you are going for over a week, as the daily car rental prices are rather high. lately we've been doing just that: we get a car for a week, doing every we want outside of WDW during that time, then drop the car off. for the next 3-5 days, we do a few days of the dining plan, enjoy our resort, and take WDW trans. it works out perfectly for us
