The camping passes can be a great deal. You just have to know what you're getting into as you get into it!
Given that your primary destinations are NJ and MA- you might look at the Thousand Trails "Zone Pass". It gives you 30 nights or so included in the fee. After that, extra nights are really cheap (like $3/night). There are 2 important catches:
1) The locations are fairly limited (see locations on TT site
2) Once you stay 4 or more nights at a park, you have to be out of the system for 7 nights. Meaning, you can't stay a week in NJ and immediately go to MA and stay for a week. There's an upgrade, but it's significantly more expensive than the $500-ish for the zone pass.
There are programs and clubs like Passport America who you buy in and then get discounts on overnight stays. The catch, as far as I can tell is that the discounts usually only apply mid-week (e.g. Sun-Thurs). Same with this, you have to check locations to see if they're places you want to go.
There are other clubs like this. Each one has a nominal fee to join up. Just read what you're getting into. They're only worth it if you use it