Well, there is 'optimal' and there is "when CAN they"...I think 6-8 weeks is great for socialization purposes...they can be with the mommy cat, and learn all sorts of appropriate and inappropriate play gestures. For weaning, though, I think a minimum of 4 weeks...but I am not an expert. Keep in mind weaning is different then placing the kittens in loving homes.

And, maybe this momma cat should be spayed?? I say that since they aren't sure of the timing themselves, maybe this was an 'unplanned' pregnancy? I am not being mean/harsh, I just hate to see more kitties brought into the world...