Weddingbee boards

Can you just say you are basically eloping and that it is only going to be your parents going? (Or whoever the 5 are.) If people are looking for a Vegas vacation, let them figure that out on their own. If you cave on saying sure come before hand, it will be weird for all of those people to be hanging around and not be invited. I'm afraid you'll end up getting roped into having a larger reception than you intended. I would just not say anything about them going.

No matter how large your wedding is, there will be people who angle for an invitation that you weren't planning on inviting.  If you really want a small, private ceremony, it's okay to just tell people that.  It's not that hard to say politely.  Just tell them that you're really flattered that they want to come, but that you're only having a few family members.  I'm also afraid that people who come along with expect that you will be hosting some kind of event.  And it seems awkward to tell people that you're having basically a private ceremony, and no reception, but they're welcome to come hang out in Vegas that weekend anyway if they really want to.

What you're probably seeing is less that everybody wants to go to Vegas, and more that people are excited about your marriage and want to be somehow involved.  You might think about throwing an open house reception when you get home.  It doesn't have to be fancy or expensive, but it will let everybody help be part of the celebration.