This is especially important if it involves selling tickets or securing sponsorship. Have a plan of action: who will do what, and when. Does the date clash with any other local event, or with anything that may make people reluctant to participate on the day?
e.g. a major (televised!) sporting event?
Once you have the date confirmed, tell everyone about it. Send out an email and advertise it on notice boards. The earlier you confirm a date the better.
Appearing this month in 1943
Title: Macbeth Author: William Shakespeare