The magician shows a picture of a top hat. A rabbit magically rises out of the hat bearing a "Happy Birthday" card. The picture is then torn off, signed, and given to the birthday child.
I have added an extra feature to Birthday Cardiographic Lite. In this version, the rabbit not only rises out of the hat but can duck back inside too. This allows a "look don't see" sequence where everyone can see the bunny in the hat except you, a plot known to delight kids worldwide! After that, the rabbit rises to his full height to reveal a Happy Birthday message that you tear out and give to the celebrant.
Consider this for your closer, get all the kids to sign the birthday card and, while they are busy with that, make an uninterrupted exit.
Birthday Cardiographic Lite resets in a flash, comes with 30 giveaway pages, and written and video instructions.