First of all, these are all deatails that should be discussed and decided on BEFORE breeding, along with researching the breed and being aware that there is no such thing as a "teacup" Yorkie. It's a term used by unethical breeders to describe dogs bred to be extremely small as adults...NOT responsible breeding.
You really are not going to be able to determine much about the pups at such a young age. I would say at 8 weeks, minimum, you *might* be able to make a decision about which you'd like to keep. Don't feel pressured to pick now. They shouldn't be released until they are around 12 weeks of age, so you have plenty of time to decide. If the other owners are aware of the situation, then they should learn to deal with it. If they don't like it, tell them to look elsewhere.
Between now and the time you need to make your decision, I would recommend educating yourself on the breed standard and how to determine if a dog is a quality specimen of the breed. (Again, something that should have been done BEFORE actively breeding.) Being educated on Yorkies will enable you to make a better decision when you are trying to evalutate the dogs.