I have said it before and it sounds mean but you essentially have to treat the families like toddlers. Be very clear, very consistent and kind but firm otherwise they try and run the show!

She texted to say they'd be late...which is more than most families will do.

Unless you have explicitly (written and verbally discussed) your expectations for drop off then most families will assume as long as they come after your start time they are in the good.

You just need to set really clear expectations. If you let them come late for your interview without discussing it after then you give the impression being late is ok. If you don't set clear drop off times, they can't know what you think is acceptable. if you accept the child without all paperwork after telling them you need it all then you give the impression you don't mean what you say.

It is up to you to terminate if you feel it is best...but it sounds like you haven't clarified your expectations and you haven't given them all the info they need to stay in your good books. Until you have done that then you haven't really given them a fair chance. The next family could be worse or the exact same it is up to you to be very firm, very clear and very consistent in what you expect and what you accept from your families.