It's not that far.
Coming from Atlanta:
Take I-85 South to Exit #69 (just past the airport) and then follow the South Fulton Parkway signs (the 2 left lanes). Go straight on the SFP 16 miles to the intersection with Cochran Mill Rd (the road narrows to 2-lanes as you pass Rivertown Rd).
Turn left on Cochran Mill, go just under 1 mile & turn left on Wilkerson Mill Rd. We are the first drive on the left around the curve and over the bridge ("to Grandmother's house we go").