I've used a tethering app before when we were on a trip. everyone was able to use my unlimited data. No one could see my actual device or anything on it or even tell where I was. It was just a wifi signal that they latched onto. I could tell how many were using it but not their IP or anything device specific for them.
the password for the assemblies could always be Ray_Franz. That way apostates or posters here or people who gossip about what they read here would know the password and you could tell how many devices were latched onto your wifi signal and know that they knew the password...
No one will look around an assembly or convention the same way again.