A lot of great stuff on this link: Best is a link to a QR code generator - those square things you can scan with your phone. You can input clues and it Will generate a QR code you can print and the Kids can scan them for a treasure hunt!
Use this FREE DIY printable decoder wheel to send & receive secret messages without anyone being the wiser. A great resource for teachers and homeschoolers for spelling practice, math, writing activities, word work, etc. Also makes a wonderful addition to
We can use invisible ink to write each letter of GHOST at each station. Make Invisible Ink To Write and Reveal Secret Messages: Iodine solution reveals invisible ink messages written using corn or potato starch.