Ugh...so they already started???
It is ALWAYS better to NOT get started with a family then to have to terminate them later.
Write up a letter. Put it in an envelope and hand it to them at the door. Then expect a phone call later.
Trust me, once you hand over the letter it gets MUCH easier because it is all set in motion now and you can't stop it.
Your first termination is the hardest. Everyone after that gets easier and easier.