Setting up for large groups:

Set up a physical barrier to prevent players watching other people ahead of them. You will need assistants to reset the playing field between players. You can also set up multiple hunts at the same time, so each player/team has their own hunt. The treasure can be a small prize in each chest or a raffle ticket in each chest that may be picked at random for a larger prize.

You can also expand the playing area as big as you want, by making copies of a grid map and having most of the hunt virtually until the grid is narrowed down to a single square. (Just remember to change the clues to say spaces instead of paces) When the hunt is narrowed down to a single square, it continues physically at the narrowed down location, with the final clues. You will need to reinforce clues and maps for wear and tear. The more creativity you add to the playing field, the better the experience!