I agree with Gayef, if they are all gaining normally and doing well...no need.
My cat had 8 kittens and I did try to supplement a little bit (just was paranoid that one would not get enough, LOL), but in the end they were better off just feeding from Mama. And they are all healthy and happy now at a year and a half.
I do think it is really important to weigh newborn kittens daily, regardless of the litter size- but especially with a large litter, because weight loss can be the first sign of something going wrong. Early intervention is usually crucial for treatable illnesses in newborn kittens. Weight loss is a sign that something is not right.
I would always suggest having KMR on hand regardless, if only as a supplement for the mother cat. Especially with a litter that large, probably most important thing you can do would be to make sure mama cat has access to quality food and fresh water at all times. I did that and also gave mama cat a can of wet food with some KMR poured over it daily, while she was nursing. After all, her milk production is a reflection of her own health, the pregnancy and then feeding that many kittens is definitely taking alot out of her.
Good luck with your new cat family!