Again, I know nothing about these areas buttttttttt...........
Cracker Barrels tend to be right off the interstates and frequently have long RV parking spaces, and if they do not, you usually can get space off to the side or back and not inconvenience anyone else.
Just a quick glance shows one at Cave City, Kentucky, Exit 53, right across the interstate from Mammoth Cave National Park, and right next to the Cracker Barrel is Cave Country RV Campground, that bills themselves as a "big rig" park and gets lots of good reviews on Google.
Cave Country RV Campground
Don't know anything about it, but sounds good and you got two choices at one exit. If its just quick overnight, campground may be more trouble than its worth. Many of the Cracker Barrels are situated in somewhat dead ended areas which discourages troublemakers from coming in, and CB encourages RV overnight stops with them.
Also a CB at Exit 2 in KY, just north of the TN/KY border, secluded and has RV spaces behind the building.
One at Exit 22 in KY, Bowling Green, directly across the interstate from Camping World Headquarters, and has RV spaces behind the building (away from the interstate, side).
At exit 48, Park City, KY is Diamond Caverns RV Camping | Thousand Trails RV Campground in Kentucky
, reviews are so so, but for one night...... or about eight miles off the same exit is the Mammoth Cave NP campground.