Treasure hunts that involve interactivity
If you have spare volunteers to plant around the place who can dress up or give out a clue then that adds an extra dimension.
Another way is to introduce more technology. Incorporate a script and a phone number. Call the number and stick to the script and you’ll get a response. Even getting people to sing down the phone can be more entertaining for fellow hunters.
Texting, QR codes and websites are another rich source of clues and feedback.
Finally, using actual people such as barmen, shop keepers or actors make the world of difference.