For your 50th Birthday party theme, here is a game idea that can be altered to fit the 50th Birthday party theme.
Check out 50th Birthday
Party Games for more free party games. A half of a century of life is a perfect excuse for a party (not that an excuse is really needed.)
DOMINOES: As the players (boys and girls) enter the hall, they are given dominoes cut out of cardboard. They pin it to their clothes. There are 2 complete sets of these cards (28 pieces in each set). The cards of one set are given to the girls, the cards of the other set are given to the boys. If there are more than 56 persons at the party you may take 2,4, 6, 8ůmore numbers of the complete sets. Before the dance begins the players at the leader's signal make pairs according to the principle of dominoes. C.f. the boy with the card 5-2 may ask to a dance a girl with the card 2-6; 2-4; 2-3; 2-0 or 5-6; 5-4; 5-3; 5-1; 5-0. Sometimes the leader may announce the change of the partners. (In this case the leader gives advance notice to the guests about his/her intentions while they are dancing). Then all the pairs change, make the pairs according to the same principle.