The month of December is a stressful month for children. It leads to squabbling. My father said they opened 1 gift on Christmas and the rest on New Year's Day. The New Year's angel came to our house starting the first of December.
One of the children would receive a gift. It was given to the one who was a peace keeper along with a note telling why that child had been given a gift.
After Christmas when there was nothing to motivate them until they went back to school, the New Year's angel came to my rescue.
She left notes or pictures or anything I could think of to keep my kids trying hard to get along. It was a big deal to get her gift.
She even told them she was watching and would tell cupid what she saw and then cupid told them he would tell who would tell the "pinch man" [candy man] who would tell the easter bunny who would tell.
It trained my kids to get along throughout the year. I cannot remember many problems.