Is he using a regular deck or a large deck Paddy?
He uses a regular deck of cards. The whole routine is just a simple force and the kids come up to help him. He brings up 2 or 3 kids which of course can't get the right card. When he brings up the last kid she get it right but the whole audience says it's wrong. He then proves to the kids that it is the correct card. How, I won't go into but it is a great effect that runs for at least 5 minutes and every kid stays interested and has a good time.
In fact he says in his closing comments that he tells the parents not to expect quiet during the party. He warns them that the kids will be LOUD!!!! and they are, and they all have fun, even the magician.