You say that people can go if they want to, but have you actually invited them? I only ask because you said in your first post that you are going alone. If I was your mil I might feel that I was muscling in if I came without an invite. Is your mum going?
It's fine to want a small wedding and I sort of wish that I had done that, but your plan just means that your guests are having to pay a lot of money if they do want to attend, even if you are saving money. I know that many people won't agree with my viewpoint, but I think weddings abroad can be problematic for this reason.
I probably wouldn't be madly keen on attending a wedding in Las Vegas, but I would go if it was my child getting married and I was invited. I would be incredibly upset to miss one of my children's wedding ceremonies and a party afterwards wouldn't quite make up for that.
Obviously if a Las Vegas wedding is what you both want then that is up to you, but there are other ways to save money. Our wedding was ridiculously cheap and cheerful. Lots of guests, but not many frills.
Oh and I would never throw my toys out of the pram whichever way my children decide to get married. One had hers last year and I'm pretty sure that it was just wanted she wanted. The other will probably have something completely different and I'm looking forward to that one too.