Are you looking to camp at the tracks or a camp ground? I can't think of any track that won't allow campers over night on race day. If you are looking to hit as many track as you can in a week time frame the Keystone Cup (Memorial Day) or PA Sprint Speedweek (4th of July) will get you to may tracks in a week.
You might also want to check out The Eastern Museum of Motor Racing at Latimore Valley. Time your trip at the right time and you could also catch the vintage cars on track too.
www.emmr.org
Let me know if you have any other questions and I'll try and help out.