AWESOME! We did a Myrtle Beach, SC to St. Augustine, Fl vactaion two years ago. We stopped in Myrtle Beach, Charleston, Savannah & St. Augustine over a 2 week period.
Myrtle Beach - I liked staying in NORTH Myrtle Beach over Myrtle Beach. Not as congested. I can not remember the name of the place we stayed but I can look it up. We were in a condo right on the beach and could walk to several places to eat and shop. Reasonable as well. We don't do the high tourist areas that are gimmicky so we avoided Boardwalk and all of that. I can do that stuff at home. There were several great places that are local "dives" to walk to to eat from where we stayed.
Charleston - LOVE Charleston. Stay in the Historic District. This way you can walk to the areas down there to see (parking down here is TIGHT). Staying in this area you can park your car when you arrive at the hotel and not get it again till you check out. You will have to drive over to any of the islands or the historic forts though. We stayed at Harborview Inn and I highly recommend it. Beautiful hotel across from the harbor, free breakfasts, afternoon wine & cheese, fruits available all day in the lobby and "courtyard" areas. Visit Rainbow Row and just walk the historic streets to see the beautiful old historic homes, the Charleston Gates, the courtyards and gardens, etc. Take a horse & buggy ride to learn some of the historic areas and their meaning. Make reservations for that and there are coupons for it.
Savannah - LOVE Savannah. Again, stay in the downtown area close to the river so you don't have to drive down there and fight for parking. We stayed at the Days Inn. Not your "mothers days inn". Very nice actually and I do recommend it. I unknowingly booked us the "Paula Deen Suite" and I DO recommend doing that (found it on either Expedia.com or Travelocity.com). What it is: They pick you up at your hotel and you go on a "Paula Deen Tour" and they drive past all of the spots that she visited, lived, operated something, etc as well as other high spots in the Savannah area. You stop at a produce stand that she shops at and can get fresh fruit, preserves, etc (the peaches were YUM). Then lunch is included at Uncle Bubba's and if he is there he comes out to visit. By doing the tour you aslo get a phone number to call to RESERVE yourself a time to dine at her restaurant, Lady & Sons. Everyone else has to go stand in line for hours to get a reservation, you don't
. The downtown river area is nice as are all of the squares. Staying in this area lets you be within walking distance of many of them and the tour takes you by many others. You can also take the trolley tours to see the high points of the area.
Can't help you with the other areas to the north but have FUN!!!!!
Oh, Hilton Head Island. Been there a few times as well and we do like it a lot. If you like to golf, tennis or ride bikes this is a great spot to go to. We stayed at the Hilton at Palmetto Dunes. Very nice hotel and grounds right on the beach. Many hotels, resorts and such are gated on HHI. You can't get thru the gates unless you live there or are staying there. Palmetto Dunes is one. You can bike on the beach on HHI as the sand is hardpacked. There are bike trails all over the island and under road crossings for the main road down HHI in some areas. Not as historic as Charleston or Savannah but a great place.
Beaufort, SC is another great town/city to visit. Very historic but not as built up as many others. The architecture is amazing.