They called you names and were completely obnoxious. They are going on mat leave and most likely pulling their child from your care as soon as it is convenient for them. They want to use you for a few months. Of course you should terminate. I'm sorry but those are the facts so take care of YOU.

I would advertise, fill the space as of 2 weeks ahead so you can give the current family the 2 weeks notice and they will probably be rude again and if you can get them out immediately that may be your best option but it depends on your contract.

There is no way you should ever allow anybody to show any kind of disrespect to you EVER! It always makes me very angry when I hear a story like this.