Hopefully, prior notification to the local LEO of an event where there is going to be an above average number of armed citizens congregating would help determine the level of a response to a 911 call.
Do you call the cops to tell them your church is going to hold services on Sunday where the preacher will deliver a sermon saying living beyond one's means is just as bad for the government as it is for a family?
Do you call the cops to tell them that next Thursday Mrs. McGillicuddy is going to teach third-graders about how a law comes into being?
Even worse, do you call the cops to tell them that you and your friends are going to meet at the gun club/indoor range/ your abandoned quarry range (the one on your own property where your family have been shooting since at least grand-dad's time) to do some target shooting and maybe some practical shooting?
Why are you suggesting that anybody needs to notify the cops that they are planning to do something perfectly legal and non-confrontational?
Had you suggested that someone discreeetly check with the restaurant management to ensure that they 1) can accommodate the expected number of diners and 2) that they are not opposed to lawful open carry, then I would say those are good suggestions.
But to suggest that one ought to/needs to notify the cops ahead of time that they are going to do something legal because it might scare the horses? Never!
Since nobody bothered to mention a "Gun Ownership Is Not A Crime" parade, or a neighborhood litter pick-up, we are not going to discuss those things. Parades usually require permits, and litter pick-ups usually are coordinated between 2 or 3 municipal/state agencies to ensure proper resource management, traffic and participant safety, and even that PR opportunities are not missed.
stay safe.