>That's not how WiFi works. They cannot know for a fact that these WiFi hotspots are within the convention space, they could and likely are, blocking WiFi located outside of that space.

To play devil's advocate, some APs support rogue triangulation. Ours plot any rogues on a building map so we know exactly where they are. When combined with a proper wireless survey, you could ensure that they don't deauth anything beyond the building perimeter. Not that I recommend that, since at the very least someone should be able to tether their phone if they want. But also because it puts additional overhead on your APs, which are usually already taxed in high-usage areas.