Here's a unique birthday idea to surprise. Get a bunch of sky lanterns, we got them online, got them delivered. Call your friends over, show them a demo how its done (its not big deal to light one up though) and when the birthday boy/girl comes out of waiting, everyone's ready with big beautiful shiny sky lanterns, which float into the sky, lighting up the sky with little illuminated dots. Make a video and its memorable :)
Let me know in comments below, if you tried this
Shot on the iPhone
Music: iMovie on the mac