Phil,
Life is what happens while you are making plans......
I don't have much travel time you can use, but some years back, we went to the Balloon Fiesta via RT-66. It was actually largely I-40 as Rt-66 has been de-certified.
Were You (and I nearly am - I have the fist of two procedures next week) I would ask the planner programs for a good route and then change it to make it the time you want to be on the road.
You can take the northern route on the backhaul.
Suggestion: Traveling in late season, maintain provisions for at least 3 days. If the weather turns to "stuff", plan to hunker down somewhere and wait it out. That can easily be a day, and two is not unheard of, but that third is just a safety buffer.
Some years back, this happened to us. At this time I have forgotten where exactly. It was not a highway rest area because when we got to the first one it was FULL. Where ever it was, we had a good view of the interstate and were warm and cozy in the coach except when one of us had to take the dog out...
Matt
Matt & Mary Colie
A sailor, his bride and their black dogs (one dear dog is waiting for us at the bridge) going to see some dry places that have Geocaches in a coach made the year we married.