Devils advocate here....
I call your business and say I heading over with a gun which I can legally possess. Manager is a hoplophobe who calls law enforcement. Weapons are banned, you are hasseled, what was gained?
Versus showing up, manager comes to speak with you, you inform him of the laws and he either allows you to carry or has you leave.
PLEASE, no more phone calls to businesses... Never alert them you are coming.
We have had a few OC meets and a bunch of us have met for dinner/lunch at various Applebees in the Puget Sound region. To my knowledge we have never been asked to leave. While your heart was in the right place, I only see this causing issues down the road.