in regards to the restaurants, there are many, many great independent restaurants. Charleston is a foodie city for sure with some pricey places, but there are also some gems that aren't as expensive. I totally concur with Bill about Hominy Grill --- AWESOME each and every time. Here are some more favs:
DOWNTOWN (more expensive):
Steaks --- Halls or Grill 225. Both are STELLAR.
Seafood --- Hanks. Unbelievable for 25 years. Very fresh & very good.
Upscale-Down South --- Magnolia's & High Cotton. Both are very good & not near as pricey as Halls or Grill 225. Husk is in this category to & EVERYONE seems to love it, but me. It's good .... just not as good as the fuss IMHO.
Down South w/ a Flare: Hominy Grill as mentioned above. Great prices for the quality too. Better than Husk.
Urban Feel --- Cypress. Innovative menu, but very good. Owned by the folks who own Magnolia's
SULLIVAN'S ISLAND:
Burgers --- Poe's !!!! Simply a must if you love funky places with a cool vibe. The burgers are amazing.
MT.PLEASANT:
Upscale-Down South --- Old Village Post House. It's a very small, quaint Bistro located in the Old Village which has a New England feel to it.
Seafood on Shem Creek --- The Wreck of the Richard & Charlene is pretty damn awesome, BUT it's hard to find, they don't take reservations & they are always semi-rude ..... to me anyway. You also have several others:
RB's on Shem Creek --- great to have lunch & a beer on the deck and watch the dolphins scare the shit out of the paddle boarders & the kayakers.!!
Red's on Shem Creek --- Food is not awesome, but a GREAT place to have a cold beer & some BBQ Bacon Wrapped Shrimp AND people watch !! Next to RB's
OK .... enough for food !! What to do? A lot !! However, for free ..... just enjoy walking the Battery, the shops on King St., do the Market. A sunset sail on "The Pride" is very, very nice & romantic.
Hope this helps. I have hit on a few. Lots, lots more ..... but this will get you started on your research. I would suggest finding a lucky guy to spoil you some while you are there !!!
Enjoy & Safe Travel