If you were to do an event, I would make it cross realmed, not 1 single server. A lot of people wouldn't reroll for the occasional event. Last time, we just got a few p2ps and crz'd everyone who was interested into a group. We played in zul'gurub (which is nice because there are no mobs in there low level and when you die inside of it, you get an instant res right outside the instance) and in Ahn'Qiraj (which also has no mobs in it). You need to find a spot, think of an objective (capture a point, straight up deathmatch), and organize it on TI, get people to back you.