I was going to say the same thing !! I would probably having a conversation or send a text to both stating they need to get their schedules in order without your involvement ! I would also state the contract signed was for four days a week and if that is breached it is cause for termination ! So you can fill the spot with what you would like instead of waiting for them to decide what they want !!
I'm sorry but I would not be sympathetic to a man who is telling all his business and making mom out to be the bad guy ( not saying she isn't ! But this is entirely too much information )