For your return trip the idea of I-64 to I-81N is a good one, but you should also consider I-64 @ Lexington to Beckley WV, then north on I-77 to I-70 To Columbus then 270 to US 33 to I-75.
The Lexington VA to Beckley is hilly and a very good scenic drive, because you will be traveling "over" the mountains, Beckley to Parkersburg WV (I-77) is less hilly, however you are traveling "on" the ridge of the mountains and from Marietta OH to Cambridge it flattens out until you get to I-70 west where it is flat to Columbus and points north the OH/MI state line.
Good Luck
