If your last name ends in "feller", "nderbilt," or "uffett," by all means send out invites, get a firm guest list, and provide travel and accomodations to your lucky guests.
Otherwise, could I possibly convince you to reconsider your destination wedding?
Are you trying to bankrupt your guests?
Do you have any connection to this destination?
Do your guests?
If the locale is one that is meaningful to a large percentage of your guests, then go there the way that you all always have gone there in the past, nailing down travel and accomodations farther in advance than usual.
If the locale has no connection to your shared life together of the lives of your guests, I beg you to at least consider one potential wedding location that does.