How about going for a real Italian dinner on the Hill? I don't have a particular restaurant to recommend, though.

Take a walk through the beautiful campus of Wash U, then go to the Loop for burgers at Blueberry Hill? Check out if Chuck Berry is performing when you are in town. The Botanical Gardens are nearby, too.

Kirkwood and Webster are beautiful neighborhoods with quaint little downtowns. Dewey's has locations in both places. Wonderful salads and pizzas.

If you go to the Arch, people might want to walk over to see the 'new' ballpark.

Busch Gardens?
Clayton shops?
(St Charles? Don't think I have heard much about people going there)

Next week the city will be crazy will Cardinals fever. The games should be downtown on Wed (3:00 game), Thur & Fri (7:00 games) so unless you want to get caught in all of that, I would suggest staying out of downtown

Will you all have cars? Public transport, especially to/from where you are staying is very limited.

For fist time visitors, the arch is always an impressive sight. Forest Park offers the zoo, the Missouri History museum, the Saint Louis art museum.

Plaza Frontenac, across the street from the Frontenac Hilton, is certainly a place for shopping (Saks and Niemans)and also has a good, "art film" movie house if you need close by evening entertainment.
http://www.landmarktheatres.com/market/St.Louis/PlazaFrontenacCinema.htm

I don't often go to St. Charles, this is the website for the city. You certainly need a car to get there.
http://www.historicstcharles.com/

I can't think of any reason for a visitor to go to Union Station. (I'm sure the city tourism board would hate me for saying that, but I can't think of anything there that really is worth seeing, unless you just want to see the architecture of the building).

St. Louis doesn't have a Busch gardens. We do have the A-B brewery where you can take a tour, and Grant's Farm (owned by the brewery and home to the clydesdales Grants Farm is now on fall hours and they close at 2:30. Not sure how that works with a group in town for a conference.

http://www.budweisertours.com/z01/

http://www.grantsfarm.com/

Sorry-- I meant Grant's Farm!

You might want to drive up to Hannibal, Missouri to see the hometown of Mark Twain (Samuel Clemens).
We love Forest Park which has the Jewel Box, Science Museum, Art Museum, Missouri Historical Society, the St. Louis Zoo (which is wonderful).

You might want to see a Cardinal Baseball game, the old Federal Courthouse (the famous Dred Scot Decision), the Arch, river cruises (I think they have gambling), and yes Union Station unfortunately, is not that great anymore.

There is plenty to keep you busy in ST Louis.
The ARt and History Museums are great and I think both have special exhibits now.
The FREE zoo is great - and one of the top 5 in the country.
The best restaurants are in the Clayton area - 5 min from where you are staying.
If you want reccomendations I have plenty!!
If you want funky - go the the Loop on Delmar in University City.
Lots of great boutiques on Clayton Rd near your hotel!!

There are some close wineries - some only 30 min away! If that is of interest let me know!

The best thing about St. Louis are the people!