My fiance and I decided a month ago we're going to be doing a destination wedding to Jamaica!

We were fine and content of it just being the 2 of us because we know that expense for guests could be pretty high.. in fact that's what we told everyone the first 2 weeks! However, we have friends and family saying they would love to go to the wedding!
My question is, should I send out save the date cards letting everyone know it's an open invite or should I actually send out invitations? We're not expecting anyone to go, but would like everyone to know they're welcome if they would want to attend! The friends and family that have decided to go is also going to be making a vacation out of the trip as well!
I just put this up on the etiquette board as well so I'm going to add a few things into this!
Since we've told everyone that it's just going to be the 2 of us, people already think no one is invited, and that's why we're thinking of doing the open invite! The resort we are choosing includes up to 30 people with the package *as far as reception and what not* and I don't see that many coming.
I'm just not sure how to handle this situation now! Any advice is welcome

Hope everyone is having a nice day!