I would do long term parking or use one of the private lots close to the airport. Many of the private lots offer coupons (google search).
Your car service will be expensive when you factor in return trip (from Newton)-- I'm guessing at least $150 each way.
Another option would be to check with a hotel near the airport to see if they'd let you leave the car there if you stay overnight prior to departure-
I agree with dwrrn, drive yourself and get a room near the hotel the night before. There are many private long term lots near EWR, I use Corporate Parking http://www.corporateparking.net/ which will run you about $13/day + 15% tax less a 10% AAA discount if you're a member of AAA
-:- Message from TripAdvisor staff -:-
This topic has been closed to new posts due to inactivity. We hope you'll join the conversation by posting to an open topic or starting a new one.
To review the TripAdvisor Forums Posting Guidelines, please follow this link: http://www.tripadvisor.com/pages/forums_posting_guidelines.html
We remove posts that do not follow our posting guidelines, and we reserve the right to remove any post for any reason.