The girls would probably be fine as they are used to playing with each other. However, I think I would pass on them just because of what you are saying about the mother. Why is it so important to her for you to be registered? How does it make your abilities as a caregiver any different? If she is already trying to push you around, and she is just inquiring about care, that is a red flag to me, and I would pass. She may be the controlling type that will always find something to complain about.