We take most of your proposed route except we go in Jan so I stay on 59 till I get to 10. Your route may be better this year with the flooding in Houston, we were taking 105 in Beaumont to get around Houston. Will have to check on campgrounds, some were closed last year from floods, got to be a lot worse this year.
FWIW, there were no trouble spots on the I-81 route last winter. Well, maybe the Harrisburg PA, quite a bit of traffic.
We've also taken 90 in San Antonio to Van Horn just to get off the highway for a while.