Thanks for you advise - I'm not worried about being the bad guy - I'm always the bad guy and I am used to that now. I always say (not to my son) that I am the parent and daddy is the playmate. I just don't like that I have to be put in the position of dissapointing my son. I will - there is no way I am letting him go to the other sitter - it just stinks because he was looking forward to that and it's hard to know where to draw the line on what to tell them.