[this line of the reply has been censored by the author]
I personally don't approve of the prior notification to it, as I'd rather it all be spontaneous and novel; if you have an idea about what's going to happen, much of the fun and interesting-ness is removed. It shouldn't be, "Hey, if you're here for this event [festival] on this day [the 32nd of February], be prepared for fun!" My character, and myself, would intentionally avoid that area.
If there were just little bits of /game text thrown about in the village squares (A small group of tiny folken walk by, huddled closely as though guarding something important), both myself and my character would be more inclined to follow it and play along (and we would ignore the players who would no doubt insist on breaking into the group and stealing whatever treasure they perceived the group to be protecting, unless the gamemaster incorporates it into the session).
That said and explained, being able to set something up with a clan leader, as Asadi suggested, wouldn't be that bad. And I'm interpreting it as an event that would be confined to that particular clan's halls, not something for everyone to join in on; I'm not against these events encompassing the entire site, as I would actually enjoy that, but I know how chaotic it can get, and I think the less involved, especially for a site so large, the better.
I agree with Jinsei on the dedicated Gamemasters idea. Less for the other mods to have to pay attention to, I think, would be a good deal. But, if they have an idea they want to use, then they can go ahead and do it, I'm not saying that they shouldn't be able to, I'm just suggesting that it would be a better idea to have a few members whose job would be to instigate and create a role-playing atmosphere. Isn't that what Shinobilegends is supposed to be?