I'm so so so sorry about not getting back to you about going to Charleston.
I am so jealous, you will have a great time.
If you like seafood, hit up Shem Creek in Mount Pleasant ... its about 4 different ( local not corporate ) seafood restaurants on Shem Creek ( duh )
JBs Smokeshack is on Maybank Hwy on Johns Island ( on your way out to Kiawah Island ) ... I used to work there, it's wonderful pork barbeque.
For dessert, hit up Kaminskys on the Market. They only serve desserts/coffee, its right next to TBonz.
If you want to purchase a sweetgrass basket, be prepared for sticker shock. They are expensive, but its really worth it.
Visit the Battery, Market Street and Fort Moultrie ( if you like history )
Wadmalaw Island ( 45 minutes away from Charleston peninsula ) is the home of the only tea plantation in the US and Firefly Vodka. ( ! )
That's all I can think of now !