I am with Crayola ... as much as I dislike conflict I think this is something that should be handled both 'in person' as well as in writing ... I always put everything in writing just to cover my ass however I would first TALK to the clients as well at pick up ~ if need be arranging for someone else to be home to watch my kiddies so I could talk to them in 'private' so no drama overflows into the daycare with other kids there. I would give them the 'written letter' for their records and later reflection if need be on what I had said.