Okay here it goes - I'm holding on to two different reservations. We are going back and forth between a car and an SUV. We can squish

into a car but an SUV would definitely make the trip more enjoyable (especially after a long day at the park).
Our first reservation is with E-Z Rent a Car...I'm not so sure about them as I have not rented from them before however I was able to book a Full Size car for 15 days at $331.60 including taxes. The trick I found was to click off the reservation page and the site will give you a coupon to stay on the page to finish the reservation.
The next one I have is for an SUV. I found a really good price with Alamo using the Costco code and the Visa $30 off code. For 15 days I landed our rental for $523.76 including taxes.
We can go either way at this point - but I will keep looking to see if I can get better rates.