Camp sites at Osh are actually not too difficult to get unless you want one down front and show center or in the trees. Those get rented about a month before the show, and paid for that whole month right on through the show. But if you are willing to take one out closer to the entry gates, they are almost always available, and they have shuttles that run regularly to take campers from those areas to and from the show area on a regular schedule. There are also a couple of private campgrounds adjacent to the EAA's as well, and I haven't had any problem getting a spot in one of those either. If you are real lucky, you might find a spot with some trees for shade, which you are not likely to find in Camp Sholler (EAA campground) unless you have that paid month ahead reservation.
When I started flying in 1994 I use to go every year, but it's been down to about every other for the last decade. The airshows are fantastic the first few times you see them, but now I usually go visit the exhibit buildings during the airshow because they are a little less crowded then. They added a nighttime airshow about 8 years ago, with pyrotechnics and elaborate lighting on the planes, which is really something to see as well. The seaplane base across the lake from AirVenture is another fun place to visit if you are interested in amphibians like the Icon, or float planes, and they have a shuttle running all day that will take you out and back from there as well.
Depending on how close you want to look at things, you could easily be there the whole week, and not see everything there is to see.