Based on past experience, it's easier to get a bunch of parking spots that are together as you go north of Hampton. Either North Hampton Beach or Rye Beach. Depends what you guys are aimin' to do - compare cars or pick up teenage girls.
As for cost, meters at Hampton Beach are $0.25/10 minutes (and run 24 hours), parking lots aren't much better.

Mike told me about the meet. I'd like to join you guys, but am not sure what plans are that weekend. As far as I know, USCRA (vintage m/c racing) will be at NHIS that weekend, so it may be a tough call. Keep me updated with times/locations, it'd be nice to meet some of you guys.
~Brenda