Florida to Arizona

Add the Naval Air Museum at Pennsacola, worth the detour off of I-10, also see the Battleship Alabama in Mobile. Dip on down to NO for a couple of days and then up the river road to see some of the old plantation homes. In the Henderson/Lafayette La. area stop and enjoy some Cajun food especially some of the crawfish dishes. Secure everything in your RV, there are some rough spots on I-10.

Definitely do not rush here. It will be disgusting hot for at least 2 more months. At least nights in October will start to cool down but days will still be a little toasty.
Have a safe trip.

Hope you realize that Phoenix in August is going to be brutal hot. :)

Along I-10 but perhaps some miles off the interstate:

Gulf Shores, Alabama
Mobil, Alabama
New Orleans
Nice state parks in the 'Hill Country' around San Antonia/Austin/Fredericksburg (President Johnson's ranch tour, etc.)
Caverns of Sonora just west of South Llano River State Park
Balmorhea State Park west of Fort Stockton - cool swimming
Davis Mountain State Park - McDonald Observatory
Big Bend Nat'l Park - a little out of the way but worth it
Side trip I-10 & Hwy 54 to Carlsbad Caverns National Park, NM
Las Cruces, NM - White Sands Nat'l Monument - do it late in the day towards sunset - beautiful
Deming, NM - Rockhound State Park, City of Rocks State Park - tour Silver City area
Benson, AZ - Tombstone, Bisbee
Tucson, AZ - LOTS - Desert Museum, Saguaro National Park, drive up Mount Lemmon - cool temps, have lunch at the top - restaurants, Air Museum

Hi neighbor. We moved back to FL from AZ 4 years ago and although we were also in no hurry, we didn't see a thing worth stopping for.