The most important thing is that there is good tides, and you definately picked a good time to come. Starting on Friday, the tides are good till at least Teusday the 14th, and if you have a flat that floods early you may even be able to fish Wed the 15th (tide will be just a little late, i.e. dark).
I know that there are plenty of good wading spots in the Charleston area....I just don't know any of them. I have not had a chance to fish up there at all. I fish around Beaufort, and a little aroun Hilton Head. You may want to check on this board for some Charleston Information:
Click on the tab for fly fishing. You may have to join to get participate and ask questions, and I highly recommend you do.
Mad Mike and Nikonjedi would where I would start to get some information...people can be a little touchy about sharing info. I would introduce yourself, let them know that you are coming, and then go see them (I think that they both work at fly shops in Charleston). They would be more likely to help you with some information in person.
If you are coming to the Beaufort area I will give you some places to try out. Let me know your e-mail address and who referred you to me if you do not mind.