bake him 4 mini pies and cut them to shape 3.14 ...that could be really hard though. you could also get a few friends together and use your bodies to write out 3.14 (as in lay down in the shape of the number then take a photo) then print it out ?
or you could get a friend w/ a harmonica and bust out the following song:
Oh Number PI
Oh, number Pi
Oh, number Pi
Your digits are unending,
Oh, number Pi
Oh, number Pi
No pattern are you sending.
You're three point one four one five nine,
And even more if we had time,
Oh, number Pi
Oh, number Pi
For circle lengths unbending.
Oh, number Pi
Oh, number Pi
You are a number very sweet,
Oh, number Pi
Oh, number Pi
Your uses are so very neat.
There's 2 Pi r and Pi r squared,
A half a circle and you're there,
Oh, number Pi
Oh, number Pi
We know that Pi's a tasty treat.
(to the tune of "Oh Christmas Tree")