feed little momma
I can only imagine how hard it must be for her to get food, when she is busy protecting her little ones from predators. It would make it a lot easier on her if you fed her, and her kittens would be healthier as well because she could produce adequate milk to feed them. As far as taking the kittens to socialize them, if you take them too early, they may have behavior problems, but if you wait too long, they will, as you said, become feral. The ideal solution is to get momma to trust you as others have suggested, so that you can take her in along with her kittens.