Yes, write up a letter and remind them of the late fee and state that it will be need to pay THAT DAY! Explain that them being late, puts you and your family behind schedule and that can not happen. I charge $10 for the first 15 mins and then a full days pay, $30, for anything after that. I also added that consistent late pick ups may result in termination of care.

I also would get any child that is still there at 525 ready to go home. They can start getting their jacket and mitts on and then the parent just needs to slip on their boots and away they can go! Keep the talking to a minimum and say "well have a good night. I have to get supper ready so we can be out the door ourselves!" and walk away. I would even have your 11 year old take your 2 year old to their room or living room if that is a reason for them staying longer than needed. (I'm thinking like if their child stays and plays with yours)

Good luck!!