Your SC license is not honored in GA.
You may carry a loaded gun in your vehicle as long as the gun is in the glove box, console, or "in plain view." The courts have been so strict about "in plain view" that I would forget that option. Keep it in the glove box or console ONLY. Under the seat, between the cushions or anything like that is illegal.
You are not required to notify an officer about the gun. Personally, I would just keep that info to myself unless directly questioned about it.