If you don't want to drive downtown from St Charles then consider the
Casino Queen RV Park. It's in E St Louis. Full hook ups. It's not dry camp. You definitely won't want to be driving around E St Louis but the Casino Queen is right off I-55 exit so you're not really driving thru ESL. A lot easier to get to than the St Louis RV Park, a lot less traffic. Just outside the Casino Queen is the metro which crosses the Mississippi River and drops off at several places in the downtown area. The view of St Louis at night is pretty good from the Casino Queen. You'd be right across the river from the Arch. You will also see a lot of river traffic. If barge traffic is moving you'll see a lot of it.
If you can avoid pulling your 32 ft trailer thru St Louis you'll be happier. It can get kind of nuts. Rush hours definitely not and if there's a crash on any of the interstates thru town you can be in a real mess in short order. If the Cards are playing in town it's going to be backed up on the interstates but particularly side streets.
You could spend a couple of days downtown St Louis at the Arch, Museum, Budweiser Brewery, Grants Farm, Zoo, Busch Stadium. A lot to see in the area. Cahokia Mounds is interesting and something kids should see.
Lots of history in that area.