Exercising patience is exasperating

I tend 3 children other than my own during the day. I have no problems understanding what the children need and attending to them. Their parents on the other hand are a different matter entirely. Well no, one set of parents is trying. I have been told to expect a certain child at 8:15 every day. So I get up earlier than normal, make sure the house is clean, breakfast is ready, kids are dressed, I'm dressed, showered, dishes are done and everything prepared for arrival of the children for the day. Yesterday however this one child didn't get here until 9, no call, nothing. Today at 8:50 I receive a call saying "Oh I forgot to tell you that we have a Dr's appointment and we wont be there until close to 10". Now however I have cranky children (my own) because they get up a bit earlier than normal and have to get dressed, which they don't like to do. Unfortunately to mention this insensitiveness on their part to them would mortify them. They would be completely embarrassed, mortified and horrified. Goodness, I told them their son threw a fit one day because he wanted something and I refused to give it to him and they acted like I had told them that they were the most wretched people in the entire world. To tell them they were actually being impolite would horrify them. Sigh I guess Grin and Bear it Ness, Grin and Bear it.