If you do follow the AC route, there are two nice camogrounds in New Jersey. One at Worthington State Forest in the Delaware Water Gap. The other at Bull's Island Recreation Area just above Stockton. The latter has some really nice walk-in sites. Weekends are usually booked at Bull's Island (only open until the end of October) and I would suspect Worthington gets crowded, too. While you can make reservations, NJ state parks require a two-night stay if reserving for the weekend (Fri. & Sat.). If you show up on a Saturday and there is room you don't have to pay for two days.

Further up, the Jelly Stone campground outside of New Paltz was decent (although commerical) and empty in the fall. The state park just north of Hyde Park, NY was nice. A day off there gives you time to visit the Roosevelt home and the Vanderbilt mansion.