It's not too late! It'll be live through this coming Friday. If you reach the end you still get 5 pages worth of upvotes from me.
I've seen a few people do riddles, but as soon as the first person figures it out no one else seems to comment. That doesn't yours might not do better though.
You have to advertise heavily though. I used six memes to promote my scavenger hunt and still had relatively low turnout (only 10-15 memers started, so far only 7 have finished). I'm glad that those who did participate seemed to really enjoy it though.