From St Louis going west on I-44 towards Branson. Take exit #203 (just past Cuba! at F& ZZ exit) go left, then left again on outer service rd (ROUTE 66) to a little town called Fanning (just a few miles) to see the worlds largest rocking chair. They have a very unique gift shop and indoor archery range. A lot farther west (almost to Springfield) is the big drive thru animal kingdom. (Yes they have a place to unhook your trailer).
If you have a lot of time, you can hit a Saturday nite race at I-44 Speedway near Lebanon (Sleeper exit)It is an asphalt track.
If you want, you can take the Six Flags exit (closer to St Louis) and go left, then right (on ROUTE 66) then follow the little blue "historic route 66 signs" all the way to Rolla. Then I think it picks up again somewhere and goes again. --- Just past Fenton (before Six Flags) you can visit "Route 66 State Park" -- Please check the website first. There may not be room for trailer parking!!!
Camping World is near Springfield. As mentioned Bass Pro Shops is in Springfield (Off Hwy 65 south--Sunshine St exit) Bass Pro Shops is also in Branson in the "LANDING" mall in old town Branson. You will want to visit "Dicks 5 & 10" when in Branson too.