Orange Pi One would be a good alternative but it is not possible to source in time for workshop.
Raspberry Pi 2 / Zero
Orange Pi One
The Orange Pi is a US$15 Raspberry Pi clone.
The Orange Pi Ones are a US$10 possible Raspberry Pi Zero alternative, but not sure how compatible it would be with WiFi dongles and the applications and installation that we've developed specifically to work with the Raspbian install.