How Do You Confound A Set Of Kids Who Are Going To Stay Up Till 12 Midnight To Open Up Their Presents?

ANSWER:

Tell them that "Jesus was born at 7am. You can't open your presents until then".

I recall being the first one out of bed - 5am - on Christmas day.
I can't recall my parents' policy on opening presents at 12 midnight. They had to have one because we didn't do it.

I do recall watching the "Gumby Christmas Special" every Christmas.