Granted, there are some tough areas north and east of downtown. BUT, downtown and MOST of the st. louis area is great. Don't sell STL short!!
I would suggest an Arch (and old courthouse) tour and a Busch Stadium tour. Check ahead for times and availability. the Arch and Arch grounds just went under a major renovation (and still going on to some extent). If your kids are in jr high or under, there is also the City Museum, which is different/quirky/weird. Kids usually have a blast when they go there.
Further out from downtown along I-64 is the St. Louis Zoo. St. Louis really has one of the best zoo's in the country. If you like seeing animals, it is a must do. The Zoo is located in Forrest Park, which is the City's central park (and the 3rd largest city park in the US!). Forrest Park also has science, planetary, history and art museums, several spots to picnic, and a boat house where you can rent a paddle boat.
The brewery is south of downtown at I-55 and Arsenal. I dont recall if you have to be 21 to take the tour. If your kids can go along, it is a neat tour to do. That area also has some neat shops along Cherokee street, and Gus' Pretzels is just across the interstate overpass from the brewery.
Grants Farm has several Clydesdales to see, but that is only part of the tour. there is a guided tram tour of the farm, which includes several exotic animals, and a stop at a european-style beer garden with free beer! Across the street from Grants Farm is the Ulysses S Grant National Historic Site, which is neat. Grants Farm is located on Gravois (GRAH-voy) Road, SW of downtown.
Historic St. Charles (west of downtown along I-70) is usually a hit with the Mrs. Historic main street with several shops, brick lined streets, and several ice cream shops. Missouri's first state capitol was here, and you can tour the building.