Here's an entertaining video about calculating Pi with real pies. The three minute and fourteen second video explains Pi and how it can be calculated.
How to Calculate Pi by Throwing Frozen Hot Dogs (with Cheat Sheet)
easy visual on how to calculate Pi
I've gathered a list of Pi Day (Mar 14) resources here - activities, songs, calculating pi, resources.
Image titled Calculate Pi by Throwing Frozen Hot Dogs Step 7
Image titled Calculate Pi Step 6
Image titled Calculate Pi Step 4