Having BF twice, I think that is really early to be gone overnight -- your supply isn't really regulated yet. You'd have to be super diligent about pumping every three hours or so, and cross your fingers your LO could handle bottles for that long of a period of time and then stil transition easily back to the breast. FWIW, this time around my LO was able to do that when I needed to pump and dump for 24 hours after surgery with no issue, but it can screw up breast feeding for lots of people. You just don't know.
I'd probably go, plan to skip the ceremony and not stay until the end of the reception, just because of the drive -- at least then you still get to go, and maybe can do the bulk of your pumping in the car anyway.