Give each person one of the cards and ask everyone to walk around the room. Explain that when you call out “Family reunion”, everyone should unfold the card and try to form their group as quickly as possible.
After everyone is in a group, ask everyone to exchange their names (and their hobbies, etc.) and try to remember as many people as possible. Then everybody should fold their card together, shuffle around, and then switch cards with random participants from other groups. After people have switched the cards, they will start to walk around again, and you will call out “Family reunion” again until you decide it’s enough. After the activity, you can call out one or more participants, who think they know all (or at least most) of the participant’s names, to try and guess them all.