Sorry I didn't mention this before, but since you won't have time to stop and see the sights in Washington, there's no real reason to go through Baltimore and DC either. Just stay on I-81 after Harrisburg all the way to southwestern Virginia and use I-77 south to Columbia SC and use I-26 from there to reconnect with I-95. That adds about 30 miles of driving but saves you from the traffic in Baltimore (bad), Washington (really bad), and Richmond (not too bad). Going that way would put your second night's stop in the Charlotte NC area.

AZBuck