I just had my first birthday flight yesterday and flew on Singapore Airlines in F from SYD to SIN. B-day cake was ordered for me when I told at the time of the reservation that it was my birthday that day. - pretty lame to say that I guess. But what made it very special was not the cake, but the hand written card by the cabin crew, including the captain and the F.O. wishing me a happy birthday. The 8 hour flight flew by so fast that I was really sad to leave the plane.

I am not sure OZ has similar service, but having a B-day cake in your flight isn't so bad and not so embarrassing. I shared my cake with the cabin crew.