A few thoughts on a few parks:
I like Great Adventure a lot, but sometimes ride closures can lead to disappointment for those who travel long distances. It's a very nice park, sorta the Cedar Point of the East in terms of its scale. Lots of trees and fantastic coasters. Go on a weekday.
Do not miss Kennywood. Phantom's Revenge does not get the notice it deserves! It's seriously one of the best, most aggressive steel coasters anywhere. I liken it to a distilled SFNE Superman--a shorter ride, but just as (if not more) potent. The rapid-fire ending is unbelievable. The rest of the park is great as well, and you must stay til after dark. It lights up real nice.
If you have a Six Flags season pass, get the QBot at SFNE, as they have in the past offered some very good deals to passholders. I really enjoyed my use of the QBot there, and it seems like they underestimate the waits on those things, so a Gold one may not be necessary.
Enjoy the trip!