One trick I sometimes use if the skin processing doesn't work the way I'd hoped is to cut out the original face, paste it on top of the processed face and fade it. I'll erase the eyes and lips to leave the processing clear but play with the fade level on the skin areas. I've had some good results (with approval here) from that, it might be worth a try. I mostly use it on older models so I'm not sure how it would work on a child.
There could of course be another method that's more effective, my processing is entirely self taught and I'm not up on the correct terminology, I just do it!