St. Louis Cardinals vs. San Francisco Giants (6/5/2016 at 1:15pm) (website)

City Museum (website)
A giant jungle gym for kids and adults.

Missouri Botanical Garden (website)
Founded in 1859, Missouri Botanical Garden is one of the oldest botanical institutions in the US with 80 acres of gardens. Highlights include Japanese Gardens, the Climatron rainforest conservatory and a hedge maze.

Forest Park (website)
The Central Park of St. Louis (but about twice as big), includes museums, walking trails and historical buildings.
Entry is always free to the St. Louis Art Museum, Missouri History Museum and the St. Louis Zoo.

Gateway Arch (website)
You can actually go inside and to the top of the Arch! Recommend booking tickets in advance to bypass the lines

Anheuser-Busch Brewery Tours (website)
The tour is free and includes visiting the Clydesdales and a stop at the sample room

Molly's High School - Mary Institute and Country Day School (MICDS)
If you have some time, take a drive by the beautiful 100-acre campus of the school Molly attended from 4th grade through high school just a few minutes from the Hilton Frontenac at the northwest corner of Ladue Rd. and Warson Rd.