Larry (and Joe...

),
Can't help with the chartering, but I can offer a few thoughts on what to do while there.
(1) Anchor out at Ft. Sumter. Really. I've seen some folks say not to, but it's not so bad. Not overnight or anything, just long enough to dingy down to the docks and visit the Fort. It may be a bit of a bumpy anchorage (anchor inland of the dock) so plan for that....worth it though to visit the Fort for free.
(2) Anchor out along the Mt. Pleasant Channel just behind the what is charted as "Crab Bank" iirc. Then, dingy up Shem Creek, tie up to a dock and enjoy eating at a great local restaurant...pick one, they are all pretty good. I've eaten at several places along the creek, but R & B's is one I can particularly recommend.
(3) If you want to see stuff in the town, get a 3 day bus pass for $9 per person. Not a bad deal. The aquarium is cool, for example. If you are anchored at the "City Anchorage" there where the Ashley and Wappoo Rivers meet, there's a bus stop right across the street.