Going to a family reunion is fun and exiting, but if it is a large event you may not know everyone there. So what is the best way for everyone to feel like a family. Recently, I was at a family reunion that had four large family groups. The way they handled this was two fold. First, they color coded the name tags to separate the families so from across the room you knew that a person with a red name take was part of Uncle Art's family as opposed to the green, yellow and blue tags for the the other families. The second part was that they added a three generation pedigree chart so you could see who belonged to who. Each person filled our their name tag and attached it to their shirt.
So even family members that married in could add their people to the name tag. It gave the whole reunion a genealogy feel. So if you walked up to someone you didn't know you might know their father or grandfather then you can place them. So the baby you haven't seen in 20 years is now college age and you know his father so you can ask more about him based on the name tag.
This system beats having the generic "hello my name is:" tags or going up to everyone you meet and asking "how are you related" or "who are you parents". Having a color system give you an over view and the pedigree gives you specifics. Name tags are fun and can also be educational.
Sample of the reunion name tag.