Last time we did this it was somewhere around $20 per person with Mears, I think, but that was several years ago. Since I have been old enough to rent a car without penalty, we do that because it provides a little more freedom for coming and going as we please. Along that thread, I think parking is $8, FYI.
I had just posted earlier this week about a discount with Dollar. You would pick it up at the Grosvenor Resort (in DTD). I got a rate of $29/per day for a minivan in June. Go onto the Dollar website; put in the location code of MCOS01 and use the promo code of KISSE.
Now if it is just a few of you, then the shuttle may be a better way to go, but our party is 8 people and since we will either go 2 or 3 days, then this was my best rate for us.