Hmm..I grow most of my cacti outdoors, except if I am protecting them from winter. I guess exception for me are the Schlumbergeras, I just keep those indoors but by a well lighted west facing window.
These cacti you have are considered jungle cacti, they would really have better growth outdoors, perhaps find a part sun/part shade area. Light is very essential for cacti, though these ones in my area is okay with some afternoon shade, since it is too dry and hot here. And I think you have much better ambient conditions there in Atlanta, than what we have here, your cacti will thrive much better outdoors. So that is my suggestion now, if you can try and acclimate it outdoors now.
