Corbin KOA is open all year, we've stayed there numerous times. Since your coming down I-75 I would consider Casey Jones or In and Out. We've never stayed there, but know people who have. They are both right off 75 so you don't have the extra driving on I-10. As to getting the rig washed we use the truck wash at Cordelle, GA exit 97. Also if you have a brush, bucket and energy
DISNEY lets you wash it at your site.