Every branch forwards the same page
A reunion is organised by telephone game. The cousins' group decides on a date, each cousin relays it to their family, and by the third hand the weekend has quietly moved a day and the venue has become the barn rather than the hall. Worse, the answers never return to one place: Aunt Ingrid tells her son, who tells you nothing, and the headcount is folklore.
When the invitation is a page rather than a retelling, forwarding becomes free. Every copy of the link is the same copy, so the date and the hall are the date and the hall everywhere. And every guest, no matter which branch they came from, replies on the same page onto the same list.