I'm late chiming in and didn't read the other responses, however, we started the tradition of opening one present on Chrismas Eve morning, after breakfast.
For us it was PJ's, but really the purpose was to practice good present protocol. We still have a reminder talk about opening the gifts, waiting, enjoying watching others open gifts, expressing gratitude, what to do if you don't like a present/already have the same present..... It's less about opening the present and more about a teaching opportunity.