The St Louis Zoo is world class and admission is free (parking is not, visit there before 9am). I'll include this link from "Explore St Louis" - #12 is my favorite!
https://explorestlouis.com/25-things-to-do-in-st-louis/ While you're in St Louis, you'll need to try a couple of other treats - Toasted Ravioli and Gooey Butter Cake. Across the Interstate from the Brewery, there's a small shop called Gus' Pretzels (since 1920) - buy a bag of "Pretzel Endz"
https://www.thecrazytourist.com/15-best-things-st-louis-missouri/2/If I think up anymore, I'll add them later.