An orgy of four or more consisting of only family members. Usually a generation gap is included. When only immediate family is involved, a more descriptive name is Sunday Family Picnic. The phrase originated with a man and woman from Porto Rico who had group intercourse with their daughter and 2 sons. A newspaper article covered the story and called it a Family Picnic as the euphemism because they actually had canceled dinner plans with their friends to have "dinner with their children." There was food involved, but the details were not revealed.
"Hey Mom, lets go have a family picnic again; uncle Rob is in town. He can't wait to see you and Dad! I'm starving!"