Obviously if it is a destination wedding, you are only going to invite those closest to you. Let them know as soon as you know, and then get a response for how many are attending, so you can make plans at the other end, just like you would have done if you were getting married in your own town. You are definitively not required, nor should you pay for anyone's lodging, or air fair or anything extra. Would you pay for your guests gas or hotel room, if you were getting married at home? No, you would not! You are only responsible for the wedding itself, nothing more. Guests that really want to go will find a way to come up with the money, and would certainly not expect you to pay for them. Besides, if you did, where would it stop. Weddings are very expensive as it is and if anyone does expect you to pay for them, then they certainly do not know the proper etiquette. If there are people that cannot attend and you feel bad, you can always have a little party when you get back.