I wouldn't mind starting when the boat is getting close to the island. We've sort of done introduction posts for everyone. It would be good to have some interactions between the characters before they get on the island so they all start to get a feel for each other, ie.: who gets along which ones are going to clash.
I'm also a big proponent of posting order as it keeps everyone in the game engaged equally and basically works as a roll call every time you go around.
My .02
~P