I have sure fire solution for you all. Tonight when you go home ask your wife nicely... very nicely, to pull the stick out of yor azz that's making ya'll so grumpy.
You're in the service business, you're expected to be flexible. Projects, events rarely run perfectly or on time. Expect changes and be grateful these people are choosing to spend money with you. They have other options, there are many other cleaners out there.
Treat them like you appreciate them, even when they move appointments. Be gracious, be courteous even when you don't want to be. Your living depends on them.