Amsterdam? Now I'm envious. It sounds like you guy are in for really big fun. Something tells me the anticipation levels are going to hit warp drive very soon. A problem everyone should have to deal with at least once.
Speaking of sleeping on terra firma, I had the idea years ago to try a bare bones, no frills Lemans trip. Something along the lines of fying into Paris with nothing more than a cooler and hitch hiking from the airport to the track and back. That thought came to me 10 years ago and still has some intrigue. What's the chance of someone hitch hiking to and from the track without showing up on some militants web site with a gag and blindfold? If it's not possible, what the lightest way to do Lemans in a reasonable fashion?
Back to dirt, I highly recommend the ditches ar Road Atlanta for quality sleep. Nothing like it that I've found. A firm foundatoin and very few fire ants or pedestrians to deal with.