Hi and welcome to Yorkie Talk. Is this first litter? Do you have mentor (another breeder who is helping you)? If this is your first litter that would help a lot and yu still have time if you haven't found someone. Do you have the whelping materials ready and have you read up on how to whelp a litter? Your vet shoud be aware and on "stand by" too just in case.
Congratulations and good luck with the babies.