That would have been the end of it, for me, too!! Abusive behaviour towards me (even verbal) is a hard line. In front of the kids, too??? What if another child went home and told their parents what was overheard? If I was that child's parent, I would want to know that they were gone!!
Sounds to me like they tried to make up their own rules, had a temper tantrum when you didn't let them, and then went home and realized "Oh crap! We don't want to find a new dayhome for a few months! Quick, let's apologize..." I would be bloody SHOCKED if they stuck around once mom is done work.