If I put myself in your shoes and would have to make that type of decision.(tough one!) I would probably go ahead with the wedding as planned. We all know that when you do a destination wedding, not everyone can attend and sometimes that's one of the reason we are doing it. You were probably already expecting that a person very important to you won't be able to attend.
As someone else said, You are (and your fiance) the only one who can make this decision. But if you ask for advice, I'd say: Go for it, get married abroad and get the wedding you always dreamed of!
Hope this help, best wishes to your dad and congratulations!