Jerome is being mentioned and since you're coming from Kingman via I-40 you won't be passing through Jerome (but do go there once your RV is parked). Dead Horse Ranch State Park is an beautiful place to stay.
So... from Kingman with a 24' TT you 'could' take 89A into Sedona and on to Cottonwood. However, it's a winding, steep drive into Sedona. Just downshift before heading down. Last spring they were doing major road work so you might want to check if it's completed. A bigger issue taking 89A is going through Sedona. It's awful driving - very slow and congested.
Having said all that I'd recommend you take I-17 from Flagstaff to the Cottonwood exit. You will still have a long downhill doing this.
Have a good trip!