Here's a route to the Flight 93 Memorial. I'd take Rt 30 all the way outbound, then come back by taking Rt 26 south at Everett. Note that there aren't any convenience stores or gas stations between Everett and McConnellsburg, so I always make a pit stop in Everett. On the way out, Breezewood is a gob of Interstate gas stations, restaurants, and convenience stores, so it's a good place for a fill up and pit stop.
30 isn't great until you get through Chambersburg to St. Thomas. Chambersburg itself has some very nice Victorian houses on Rt. 11 near Wilson College. Lee was there just before Gettysburg, and it was burned by Confederates later in the war for not paying a ransom. John Brown also lived there while organizing the raid on Harper's Ferry. Route 116 south of Gettysburg was one of the primary retreat routes for the Confederates after the battle.
I've marked a couple of nice lunch spots. Some of the plotting for the Whiskey Rebellion was done at the Jean Bonnet Tavern.
For lunch or dinner in Gettysburg itself, I recommend the Dobbin House and the Appalachian Brew Pub (which is right beside Lee's HQ during the battle). A little further afield, I like the Boiling Springs Tavern and the Hofbrauhaus.