I too could go on and on about all there is to do and see in Charleston SC. It is truly one of the most historic cities of the US.
You can visit a number of gardens, Americas first 'planned garden' for one, a working plantation (Boone Hall), and others.
I you are into military history, you can visit Fort Sumter, and other forts. The Citadel, The Military College of South Carolina is a nice side visit. Patriots' Point is not to be missed, tour (self guided) of the USS Yorktown aircraft carrier with static aircraft displays, a submarine, and other attractions.
Charleston is home to the Spoleto arts festival, and is renowned for great restaurants.
One interesting little opportunity is their 'ghost tours' most of which are at night. Visiting graveyards and other places that are reportedly haunted is a definite 'not the ordinary' thing done on vacations.
Check the internet, there are a million other things to do and see!