This activity was also taken from Math Circles for Elementary School Students by Natasha Rozhkovskaya.
I love the book and many of the activities are inspired by the lessons in it. I found that my 1st grader needed some guidance in coding vs decoding the messages.
How it went:
It was hard to adapt the activity for kids who can’t read yet! Nia (5) loved cutting the wheel out and coloring it. I helped her code her name by just shifting each letter to the next on the alphabet. Now she signs everything OJB (instead of Nia) and writes NPN (for mom) and EBE (for dad) everywhere.
Bel (7) didn’t seem to like the activity. It took a while to get going. But then the day after, she finished the worksheet. Then starting coding a couple of her own messages to give to me.
https://www.puzzles-to-print.com/cryptograms/ has free printable cryptocodes to decipher if you child would like to continue this activity. It looks like some of the samples are NOT Caesar ciphers but more advanced ones.
Wikipedia. The Caesar cipher is named after Julius Caesar!
https://cryptii.com/pipes/caesar-cipher lets you code your own words and sentences.
Lgegjjgo A se kmjwdq zwjw, qwklwjvsq A se xgmfv sk owdd. Lgvsq A se ygfw. Ozg se A?