A couple of points to keep in mind.
1) Review the University of Arkansas football schedule and schedule around that.
2) Schedule around the Bikers Blues and Barbecue Festival (looks like Sept 26 - 29 this year). Not because of the bikers (most of them are probably older and slower than you) but because they fill up the hotel rooms and rates may be higher because of the crowds.
3) I’d echo the two museums - Walmart on the square in Bentonville and the Art Museum. North of there in southern Missouri there are several caves you can tour if you are interested in that. The big Walmart across from headquarters is kept pretty nice. Walmart No. 1 in downtown Rogers isn’t worth the detour unless you just want to buy something to get the store number printed on the receipt.
4) It doesn’t really get pretty going down the interstate until south of Fayettville.
5) The casinos just west of there in Oklahoma are run by the Cherokees. It’s been a while, but last time I was through the area, they were crappy compared to the Choctaws or Chickasaws. I wouldn’t bother with them. (OK, from the pictures, it looks like they may have upgraded).
The Cherokee casino in Siloam Springs is huge....and nice. Was just there in June. Went to the one in Grove Ok too. Little smaller but still
pretty good.