Hi and welcome to YT! You have come to the right place! There are many people here who are very knowledgable about yorkies and you will receive good advice. Please don't be offended by the concern expressed by owners as many have had and have seen very painful situations arise with breeding.
You seem to be a very good mommy with your concerns and the best of intentions for your pups and I applaud you for that. Try to take the advice you need and try to remember the concerns expressed by some are the result of the depth of love they have for animals.
I wish you the best of success in your endeavor and hope you will continue to keep us posted on how things are going. Prayers for your pups success and for their health and happiness. Blessings!