Mick:
I've lived my entire life (except for a few years in the military) in the general area you describe. I'm sure lots of folks will have thoughts and suggestions but one thing I really enjoy is getting off the "main roads" (US Interstate Highways) and traveling on older US Highways through some of the small towns that have much more interesting (to me) architecture, places to eat, and people to visit and chat with. Just east of New Orleans for example you can drive through Mississippi on US 90 which is a beach-side road and a beautiful drive. (It's slower than the Interstate but I-10 is pretty boring). Sadly, many of the beautiful old Southern homes along that road got wiped off the map by Hurricane Katrina but still it's a fun drive. In Biloxi I suggest lunch or dinner at Mary Mahoney's restaurant - it's been there for decades. In Mobile, Alabama check out the USS Alabama - a WWII era battleship with a very nice museum including static displays of WWII and cold war era aircraft including a B-52.
From Mobile you could take US 98 to Pensacola, and then perhaps US 90 to Tallahassee, Florida. Fairhope Alabama is a particularly nice town and a great place to be at sunset on a nice day. The National Naval Aviation Museum in Pensacola is NOT TO BE MISSED. While you're there you just might see the Blue Angels practicing. US 98 from Pensacola is also a great option - you might take it to Fort Walton Beach then drive North to Crestview and take US 90 from there.
Interesting towns along US 90 include Crestview, Defuniak Springs, and Marianna. I recently flew over to Crestview - the airport there is worth a visit with quite a bit of transient military traffic as well as a facility that de-commissions big jets (think 747, A330 etc) - I only taxied by there but it's easily viewable from the FBO/ramp area. If you're a diver, there are many springs in this part of Florida that have crystal clear water with constant year-round water temperature. Not a diver myself but I'm told they are great places by friends into that hobby.
By the way, a huge number airports in the US Southeast started life as WWII training bases (some even before WWII). The weather in the area and flat land make for great training conditions - Marianna's airport is just one of many of those old bases. Many of them have fascinating history and interesting old buildings and road networks. Flying around this area you see many abandoned old training fields - a classic sight is a triangular arrangement of 5000-foot runways that seemed to be a common setup.
Between South Mississippi and central Florida there are many active military bases and particularly training bases. These include the Naval station at Pensacola (where the museum is), Whiting Field, Eglin Air Force Base, Fort Rucker (base of US Army helicopter training), and Tyndall Air Force Base. While you can't "tour" the bases you will likely see quite a number of aircraft from the bases as you drive through the area. Flying the area is "interesting" with military training at all levels, aircraft of every speed and performance profile, and quite a bit of civil and commercial traffic as well. (If you make to Jacksonville I'd love to give you an aerial tour of North and Central Florida)
From Tallahassee I would drive down US Hwy 27 and US 441 to Orlando. Lots of small and mid-size towns along the way. Many US small towns are shadows of their former selves due to economics and people moving from rural areas to larger cities, but still much to see along the way. The University of Florida campus in Gainesville is one of the nicer campuses I've seen in the south but I'll get some pushback from others about that opinion I'm sure. Just south of Gainesville, Payne's Prairie is a fantastic natural area with lots of 'gators (and Gators) and other Florida wildlife. Nearby is a fantastic little town called Micanopy.
So much else I could think of but this might give you some food for thought. Feel free to PM me if you'd like. I'm between RV's (plan to build a -14 eventually). I'm sure any number of RV-ers would be happy to have you visit as well - looking forward to all the responses this thread generates.
