DME won't work (it was my immediate thought too) as the OP is going to the beach for three days prior to WDW.
I agree with those who say just go w/the minivan at the onset!
See, I knew I was missing something.

OP, I'd go with the minivan...if you're going to the beach first, then you'll have to pack the car at the airport, then at the beach, then again at the end of the trip. That's a lot of packing and having to struggle to make it fit. But...why not try to name your own price for a van on Priceline?