We are only paying for ourselves and have no plans of paying for the wedding party. I'm only having 3 bridesmaids and 3 groomsmen but the cost to cover the entire party is just too much. I think most of my wedding party thinks of the destination wedding as an excuse for a vacation anyways. I'm sure by giving plenty of notice to your wedding party no one will be offended.
Also, instead of paying their way you could give them a gift of appreciation for being in the wedding such as resort credit to use toward a massage, or you could ensure that the wedding party should not give a wedding gift on top of being apart of the wedding.