Race Event!

I am planning on Race event.

All is wery simple. There will be a starting line and ~4 checkpoints. At startingline we give to competitors a hint where next checkpoint is and what they must find and bring to this checkpoint to receive info for next checkpint.

So here the problems begin. We must think about these items(which they must find to receive next info) and checkpoint location(this we should do with other staff memmbers tho) and HOW to prevent competitors from using blinks. And of course the reward, because i have no idea xD

Any help appriciated!

Sry for mine bad grammar ><(i'm a bit sleepy)