i Work in St Louis, My Mom and Dad live an hour south of Orlando AND i used to drive 18 wheelers. I have made this trip A LOT.
stop at a Wally World near Springfield Il. or between Springfield and St Louis. the cost of living in Southern Il is about 3/4 of the Chitown area. prices at Wally world will reflect that.
there is a Casino in Downtown St Louis that will let you park near the Arch, Old Courthouse and Grand Central Station. The St Louis Zoo is mostly free, and Right off I64 and has parking you can see from the highway.
Il and KY have decent rest areas, Ga IIRC has a 6 wheels right lane rule. My 30 footer has duallies so i assume yours will as well. you will not be going 70-75 miles an hour, but that's kind of the point right? I think KY had the cheap gass last time i did this run, but avoid fueling in Il if you can their tax rate on fuel is stupid.
there is really only 1 major grade in Tn and that is Monteagle just before you get to Chattanooga. trucks use low gears defined by their weight, but use the gear you climbed the hill in and you will be fine, downshift at the top and let the engine do its job.
Ga has plenty of Waffle house and Cracker Barrel for rest breaks and places to park.
i keep RV Parky and the Good Sam app on my phones home screen. both are OK for places to park and get some stuff. RV Parky lists casino's and Wal Marts for overnights or Campgrounds if you want to pay a bit more than free.
sorry for the TLDR but i hope you have fun! it could be the start of lots of family time and building memories. my Dear Wife wasn't sure she would like this but last time we were out she baked brownies in the oven while i cooked dinner over the fire.
