We always drive, but I have read on the DIS that a lot of people use a car service. From what I understand it is not much more expensive than a cab and you can stop the grocery and/or drug store to pickup incidentals before heading to your hotel.
Good idea IMO. I think it's always better to have a car available if at all possible. The biggest downside is the parking fees, but if you can do it I suggest it. Your son has a good idea there on exploring; lots and lots of stuff to do around International Drive.