Wow, that is soo far over what we do here.
The teachers pony up the $$ for the Parent Volunteer brunch because they are throwing it in appreciation of all the volunteers do for the school. The parents association doesn't throw themselves a party.
Anyone who volunteered for anything-an hour at the book fair, class parent, field trip chaperone, anything like that gets invited and they have bagels and fruit and muffins and pastries and they give everyone a little token of appreciation like a water bottle with the school's name on it or an insulated lunch bag, etc.
It's fun, low key.