Flight 93 Memorial is approximately an hour and a half drive from the wedding location. I have never been here, I don't know if there is much to see in March or not.
Gettysburg National Military Park Museum & Visitor Center
1195 Baltimore Pike, Gettysburg, PA 17325, USA
(877) 874-2478
Gettysburg is about 4 hours East of Washington Pennsylvania, if you Decide to go check this Civil War Battlefield and Museum out, you will want at least one full day to explore.