Send them a STD and invite anyway, since no matter what, they are family and will always be a part of your lives.
Whether they choose to go or not is their issue. You told them from the beginning that it is what you guys wanted. If they cannot or choose not to go, it's not your fault at all.
The thing about destination weddings is, not everyone can go, and sometimes that is why we prefer it (for me that is totally the case). If I did it here at home, there would be about 500 people to invite (hella large family). But over there, we are only inviting 150 to our DR wedding.
p.s. I'm an Iberostar bride, too!