About the only way to avoid NY and Philly is going to be to head inland. It really depends on what you are set on seeing in between your start and your end locations. Look at I-84 to I-81 through PA. Not far from the I-84 and I-81 junction is Ricketts Glenn state park
Ricketts website. When you get close to the Harrisburg area you could visit Hershey, Lancaster, Gettysburg and work your way south to DC if you want to or continue down I-81. Another suggestion would be Seneca Rocks WV area to include the Cass Railroad and several caverns in the area.
