Two weeks is lot of time. You should consider stretching it out to include Chicago, if you've never been.
While you're in Pittsburgh, definitely head up Mt. Washington for a spectacular view of the city and try to catch a baseball game at PNC.
The stretch from Cleveland to Detroit includes Sandusky (Cedar Point Amusement Park) and Toledo (Tony Packo's, very good zoo, decent art museum). From Toledo, consider a slight detour through Ann Arbor on the way to Detroit.
The drive through Ontario to Buffalo brings you near Niagara Falls. The Canadian side is spectacular.
Buffalo to NYC potentially takes you through the beautiful Finger Lakes region of NY State, the Catskills (Cooperstown, Kaaterskill Falls, etc.), and the Hudson Valley.