I find with the micro-managers and parents who lack trust you just have to be assertive and upfront with them. If I had a parent like this I would simply tell them, point blank, but politely, that they NEED to trust me and my knowledge as a caretaker or we can not continue our relationship.

Typically, that is all that needs to be said. If you are open and honest then the parents will know then that they make you feel uncomfortable.

If they don't stop after you have been upfront with them then it is time to move on with another family.