I am going to add a little here.  
Not far from the south end of the Chesapeake tunnel is the Mariner's Museum that is home to the Monitor's parts.  A great stop.
The Wright Brothers Museums at Kill Devil Hill are worth a couple of hours.  
The Ocracoke to Hatteras Ferry is free.  The Museum at the south end of Ocracoke is a decent, but not great stop.  
The Ocracoke to Cedar Island ferry is reasonably priced. 
On your back haul through Detroit, plan a couple of days for the Henry Ford Museum and Greenfield Village (co-located) in Dearborn.  This is a very good stop.  Even if American history is not a great interest.  There are several campgrounds in striking range, but none close by.  
Be ready to refuel at the duty free at the bridge.
Matt