Need help renting minivan

[DisneyMom]

Looking to rent a minivan in Charlotte, drive to Florida and return to Charlotte - need 7/21 am, return 8/1 am = I'm not having much luck pricewise. Lowest price I've found so far is $589 for that period - that's a lot higher than I want to pay! I have 3 teens (one is 6'5"!) and a small Cavelier and thought the van would make the trip much more comfortable and enjoyable - but not at that price!

Anybody have any ideas on how to get this down? I tried several of the codes that I found on various sites (Mouseavers, etc.), but I'm not having any luck with them with a mini-van. Any ideas??