My 2 and a half year old has to be "innkeeper" - do you think they would appreciate him taking in a can of heinkeen.
My 4 and a half year old has to be black "sheep" and have no black t-shirts. Do you think they would mind a dark navy t-shirt.
This costume thing is all of a bit shock to the old system, sure in my day we always used to raid the school dressing up dept!