Establish a code word you and your family (including the children) can use to ask for help (like “come get me”). These code words should sound normal but be “different”. For example, a child could tell his dad that Billy is really “sweet” to indicate that Billy is actually bullying the child. Or you could ask your spouse to get some wine on the way home from work to indicate that there is a problem at home or that you’ve been carjacked or whatever. Only your imagination should limit you. But, again, these code words should be practiced and reviewed to be sure you don’t forget them.
By the way, if you are working with children, get them involved by asking them to help choose the code words. They are less likely to forget the words and they are less likely to misuse the words is they are part of the solution. (I will leave the appropriate punishment for misusing the code words up to the imagination of the parents. You don’t ask me and I won’t tell either. ;-} )