Something else to think about... See if there are spaces availible for a smaller unit. If your camper for example is 28', you would tell the campgound (or reservations center) that, and more than likely they would automaticly put you on a spot for a camper 30' or bigger. What I have found is when you look for sites for roughly 5' less in length, it may open up sites you will still fit on, but it may just be a little tight.
I just had to do this on our fishing trip. The CG said the site was good for up to 20', but I had a 26 to put on it. Got there, and it fit with no problem.
I'm not saying you cant get burned, but chances are if you are willing to work a bit to get your camper on a site, 9 times out of 10 you should be able to do it with a smaller site
'97 Jayco Eagle 314BHS
'03 Tahoe LT 5.3L