We normally stay at a small condo on the second row in Garden City at the south end of the Grand Strand right at the Horry/Georgetown county boarder. Yall are going to actually be in Myrtle Beach proper a good bit north of where we stay. Brigadune is just a smidgen south of the Arcadian Shore area between the shore line and the Dunes Golf Course. Given that youve been in that area before, I dont think youll have any problems finding it once you get there. Since youve driven the 73/74 route before you actually know more about its condition then I do. Getting a good deal on a place sounds like a good reason for at least considering a different route, but Id also be interested in seeing what AAA suggested.
Now, if you were to go via Charlotte... There are several ways folks around here do it. Heres the easy-method:
Follow I-77 South to I-20 East in Columbia
Follow that to I-95 North in Florence
Exit I-95 onto SC-327 (Exit-170) which takes you a few miles down to:
US-76 East
From there the normal rout into MB youve probably done before (US-76 SC-576 US-501 SC-22 and your in the Arcadian Shore area). The advantage of this method is the fairly high speed limit throughout and fewer road changes. The down side is a few extra miles that could be saved (but the speeds make up most of the time difference).
You can shave a bit off of this route by leaving I-77 at SC-34 in Ridgeway, following that over to US-601 in Lugoff and then taking that south to I-20 (the rest is the same).
OK, thats the easy one. Now the Direct Route (about 3.5 hours form Charlotte) goes cross-country away from the Interstates until you get to Florence. And it goes like this (hold on to you hats folks

):
From Charlotte take I-77 South to US-21/SC-5 in Rock Hill SC
Follow the SC-5 part (which will leave US-21 after a bit) over to US-521 South
Follow that to SC-9 Bypass East in Lancaster.
Follow that to SC-903 East (on the other side of Lancaster).
Follow that until is ends at SC-151 South
Follow that to US-52 East in Darlington
Follow that to I-95 North in Florence
The rest is that same:
I-95 to SC-327 South
To US-76 East
To SC-576 (Marion Bypass)
To US -501
To SC-22
Ive driven this route so many times its just about become second nature. I could even recommend an interesting stop or two along the way. Well
You did ask.