One trick i always do at a birthday party, whether kids or adults that is special, memorable and plays quite well:
Get ahold of a blank-backed card, and on the back write "HAPPY BIRTHDAY ________ [Insert Name]" Bring up the birthday child into the spotlight to be your "magical assistant." Place the pre-prepared card ( I like to use a King) on the bottom of the deck and force it, using the Hindu Shuffle Force. It will now be somewhere in the middle of deck.
Under the pretense of looking through the deck for the card, arrange to make sure it ends up 21st from the bottom. Announcing that you can't find it, you say, "But there is one possible magical way to find it" You then have the birthday child extend their hands, and you say, "Maybe if we all sing Happy Birthday to ______ , we may be able to find ______'s card." As you lead them in the song, with the deck face up and starting with bottom face-up card, basically deal one card face up into their hand for each word of the song, FACE UP, into his/her hand. On the last word of the song, the selection (the 21st from bottom). will appear face up. (Fool with this and you will get the cadence correct).
Show the face (but not the back) of the card and ask if it's right. They will say yes and be surprised. But now for the kicker. You say, "And that's not just any card - it's a special birthday card." Turn it around and show the message and say, "Happy Birthday _______.! Let's all clap for _____ for being a great magical assistant!"