If you wanted to take the southern route thru MO on 44 you will parallel US66 and occasionally can get off the I and onto the US. Depending on interests there is the sportsmans version of the lair of the magic rat, Bass Pro in Springfield MO, about 3 hours east is a choice of neat parks, Meramec State Park with Meramec Caverns or Meramec Springs which is a trout park. You might want to check for reservations there in the park but there are several good campgrounds nearby.
Coming this way you are about 3 hours from that point to the Mississippi River. You can continue on 44 thru StLouis, connecting with I70 near the arch and cross the river. Next stop on this route would probably be an overnight on a lot but there may be a CG near Highland IL
Have fun planning,
Tim