And yes, there is a committee. A committee made up of the same wasp/bee who are on Ravec and told the Home Office to pull Harry's security. The same wasp who prevented harry from having a meeting with his grandmother after she agreed to meet up. The same wasp who lied to the queen and said he didn't know H's wife was being hounded by the press and they need help. The same one who lied about the printer.
My guess, is that they knew that it's Archie's birthday and chose that date specifically. No one else would have known or cared, including Charles. As I said on another thread Charles is probably like the CEO whose PA has to remind him of his wife's birthday and anniversaries and book the flowers, restaurant and buy gifts. The wife would do the same for the children events. Unfortunately for Harry, those PA/Wife roles belong to the spiteful Wasp and Camilla.
Church leaders like bishops etc, would drop everything upon being summoned by their leader, the King. They would cancel any events being held. They could not even secure the most powerful leader in the world with this date they chose out of 365 days of the year. The only diary that matters is Charles. Even football matches or other popular will probably be later in the evening (didn't William go to a match same day he had something quite important? He attended both. It all worked out regardless)
Harry said he would like a reconciliation with his father, so no doubt, Harry would drop everything for him if he wanted to visit. I would even go as far as to say, if Charles asked Harry for an intimate meeting with the grandkids, Harry would fly his family over in a heartbeat.