Attire should be semi-formal. Make sure you can dance in it--you might have difficulty getting Christina on the dance floor but you'll have trouble getting Carolyn off.
Do I have to RSVP?
Yes, an RSVP is 100% necessary. This way, we'll know how much food to get, where to seat you, if you have any dietary restrictions, etc.
Where can I park for the ceremony?
There will be valet parking for wedding guests at the Pennsylvanian.