I don't want to be the negative one here but if they don't want to go, I wouldn't push the issue. My experience is that we went to Vegas with our best friends who are tight with their money(on things they don't want to do). Well, needless to say, it was the worst vacation ever. They didn't want to do anything because they thought it cost too much. DH and I couldn't really enjoy ourselves because we didn't want to leave them behind. Now, when they talk about going on vacation together, we try to change the subject. Never want to do that again. So, if your friends are already complaining about the money, just wait until they get there. Hopefully, you can get them to go and have a great time. I just don't want anybody to experience what we went through.