Well at one of our family reunions, we got one of our no-nonsense relatives to go around and collect money from the crashers. She was an elder, and no one had problems coming up with the money. Although they wanted to try and make something of it at first, she was prepared and explained to them that if they didn't want to pay, they could sit, visit with the family and watch people eat!!! We laughed at that one for some time afterwards. Actually no one would have done anything if they hadn't paid, but we felt that we would nip any future actions like that in the bud, and it worked. When we had another reunion, we didn't have problems.

At another reunion I labeled the bags according to those who paid. I wasn't concerned about those who were coming late and paying in person. I figured if they didn't care enough to notify us in advance, I wasn't going to prepare for them in advance. Mind you I paid for my contributions out of pocket and wasn't reimbursed for anything. I felt absolutely no remorse about it especially after this relative brought along two non-related people who got mad when I didn't give them souvenirs.

These people are in every family and there's really nothing you can do about them. They're ill-mannered and inconsiderate and I treat them accordingly, meaning that I don't waste my time with them. Think of it this way, you're inviting them to a family reunion, not to an opportunity to free-load.