It wouldn't be that big. Just like a trivia caching event. You get the coords for the first station, find the envelope there, and read the trivia question. There are 4 answers. Each has its own set of coords. You pick the answer you think is right and go there. If you got the right one, you will find the next envelope. If not, you have to go back. 1 neutral person will go with each group. That person keeps track of points.
3 points for right answer 1st time
1 point for right answer second time
0 points for right answer third time
-1 point for looking at the hint
It's still tentative, but I think it's a great idea.