I would avoid all Virginia beaches. I also wouldn't want to spend all twelve days in the Tampa area. I'm not crazy about Tampa (boring)....but beaches to the south are very nice. The Georgia barrier islands are also pretty but isolated. The Outer Banks of North Carolina (esp. Ocracoke) are also beautiful but isolated for a trip that long. I personally think that any trip to this part of the country should include Charleston, SC....my vote for prettiest city in the United States.

I think two GREAT itineraries would be:
1) (For a good mix/balance of sightseeing and relaxation) Fly in and out of Charlotte, NC. Drive to Asheville, NC and spend a few days there. It's a REALLY fun, funky town in the mountains with great nightlife, dining and sights. Then head just a short 4-1/2 hours down I-26 to Charleston, SC for the remainder of your vacation. There are many great lodging options in downtown Charleston. If you don't want to stay downtown (or want something a little cheaper), you should consider hotels just across the bridge in Mt. Pleasant. If you want to stay at the beach in the Charleston area, my first choice would be Folly Beach. It's a funky little town and close to downtown Charleston. Wild Dunes Resort over in Isle of Palms (even though there really aren't that many palm trees there) would also be a decent choice. Kiawah Island (just south of Charleston) is like a mini Hilton Head....but is a bit far from town unless you plan to just park it on the beach for most of the trip.

2) (Beaches with a nice mix of old and new) Split time between Charleston, SC and Hilton Head Island, SC....with a daytrip or two down to Savannah, Ga. Hilton Head is a resort island with great beaches. Savannah is a beautiful city 45 mins south with great nightlife and dining.

Just be prepared for potentially hot/humid weather in this part of the country during June....especially from SC and south. I think Florida temps could be hard to handle if you're not used to them.

Have a great trip!

Being from the area, of course, I have to defend Virginia Beach/ Hampton Roads, but depending on what you want, it may not be the best fit. If you factor in it's sister cities (Norfolk, Chesapeake, etc) you'll get a great mix - particularly for beach during the day. locals bars, shows ,etc at night. Just avoid the touristy oceanfront strip (typical of any "beach" area). There are 3 beaches in Va beach - Bay front, Oceanfront, and Sandbridge (no hotels - only homes/Condos to rent). Not to mention there are good day trips outside the area - like to Williamsburg.
www.visitvirginiabeach.com

Carolinas - you may like Nags Head, Outer Banks, but there aren't really "shows" there - more beach pubs.
www.outerbanks.org

Savannah, GA - Haven't been but it's on my bucket list. Great history, heard it's amazing but it is $$$$ www.savannah.com

Charleston, SC - GREAT area, definitely recommend it. No idea about shows, but bars, shopping and history are good. Again, $$$$, though. www.charlestoncvb.com

Hope you have a wonderful trip!