We just returned last night from Orlando. It probably makes a difference if you are staying on-site or not. We had 6 adults and 2 kids (4 & 2). We stayed off-site. We knew that we wanted to split up some days and wanted the convenience of two vehicles. The interesting thing is that I reserved 2 minivans from Dollar several months ago. When I got the to counter the agent tried to talk me into renting one 8-passenger van instead. Not only did we want two vehicles for convenience, how were we supposed to fit 6 adults, two kids in car seats, 8 suitcases and 6 carryon bags in one van?
If you decide to rent two vans, I definitely recommend two-way radios unless you already know your way around. We were trying to follow each other most of the time and the cell phone signals are iffy at times plus by the time you dial the phone for the other van, you have already gone past the turn you wanted. We bought the radios while we were in Orlando.