u say that you were already reluctant to take on this family from the get go and that you were sort of hoping they would leave once you tell them that you are pregnant so i would say go with those feelings.

You only get a week or two of trial time where you can politely say that this arrangement is probably not going to work out so do it now before you get too attached to the child or get in deeper with this family and regret it.

I have talked to providers who ended up stuck in bad situations and then they said they had sleepless nights and anxiety and there was no good time for them to terminate anymore.

Go with your instincts and like dragon said - trust yourself. Good luck