One fun reunion idea my sister-in-law did with her family was a "Survivor" themed reunion
around the 4th of July. They had all these little competitions each day that at least one person from each family had to be in - like the 4th July 5K, a watermelon eating contest and seed spitting contest, a pancake eating contest, whistling competition, etc. They all had cute t-shirts that said - I Survived the (Name) Family Reunion 2008. It sounded like a lot of fun.