IMO, do NOT notify or ask a business in advance, except to maybe make a reservation for a large group. (I feel this is a reasonable courtesy to extend in return for the reasonable expectation they'll accomodate your group.) If you act like it's a big deal, they're more likely to turn you away. Besides, would you aske permission to exercise any other right in their establishment? ("Hey, we want to hold a Bible study at one of your tables... do you care that this mightdrive awaysome of your atheist customers?" Sounds silly, right? I hope so...)
However, I think a good strategy to "beat" the Brady intimidation tactics is to plan a pre-meal event outside a business. Then when everybody shows up there you can either break up into small groups and go where you please,or even have a mass-event at a restaurant. By having anevent(e.g. litter pick-up) before going to a restaurant/cafe, you wouldn't need to make the restaurant/cafe known in advance.