If you're still checking this site....there's NJ Off Road Vehicle Park.
$300/yr for adults. $75/yr for kids. They have some very ATV'ed up trails... sandy, rutted by ATV tires. And three MX tracks. The MX are not too difficult for someone who is somewhat familiar with how to ride. It gets very busy there.
If you want a little riding instructions...
As for MX tracks, there's Atco and Raceway Park. Check out Trapani's web site.
On the left, you'll see a link called "Tracks"
In reality, there are more than just tracks listed there. But figure a 2 hr + ride for a lot of places. Rausch Creek has tracks and trails and is a fun place to go. Probably 2:45 from your area into PA.