Here are some resources to explore Pi Day!
I highly recommend starting with BrainPop. The kids love this site, it is fun, educational, and they can take a quiz at the end to test their knowledge.
BrainPop is offering free membership right now, this is a wonderful resource for kids to explore and have access to.
I hope you have a great Pi Day and enjoy some Pi or even some pie!
https://www.brainpop.com/math/geometryandmeasurement/pi/
https://wv.pbslearningmedia.org/search/?q=pi&selected_facet=grades:4
http://www.piday.org/learn-about-pi/
https://www.scholastic.com/teachers/articles/teaching-content/exploring-pi/