The Edisto Shelter at James Island County Park, Society Hall in Downtown Charleston, or The Summer House in Summerville are a few places that you might want to check out. Hope this helps -- Jay Maxwell (Jay Maxwell's Music by Request, LLC)
One of the best kept secrets is right over the Ravenel Bridge in Mt. Pleasant. It is physically right 1/4 mile from the bridge on Coleman Blvd. It is called "Tidewater Chapel". Don't let the name fool you! Even though it has a beautiful chapel, its reception area (indoors and out)is wonderful with a large kitchen and plenty of parking! Finally, It is the most reasonable venue I have found in Greater Charleston.