
If the bitch will feed them until their eyes open around 12 days, and they are gaining in the meantime then you can start early weaning by then.
I have done this if the rate of weight gain has slowed down.
I normally offer first weaning foods at 18 days, just a taste the first day then two the next until at three weeks they are taking something four times a day, and the amount will go with their needs, often very little until four weeks, but other litters take much more.
I feed pups to appetite always preparing more than they are likely to clear and let Mum clear up after.
That also encourages Mum to be interested in her pups.
I would allow her to visit her own pups and interact with them as she sees fit, after all they are her puppies and your job is the foster litter, which she is helping with.
Her pups need her interaction to learn how to be dogs, this is a very important stage so that pups will be well adjusted, when they go to their new homes, and is a stage that must not be skipped. Even if the bitch appears to have little interest she will be vey aware if squabbles break out etc and keep things in order.