1. Yell at them. This dampens the mood somewhat.
2. Tell them to clean their rooms to make way for the new stuff the could potentially get. Then tell them to clean the rest of the house as well.
3. Get Daddy to sing his mop-microphone, over-dramatic version of Silent Night. Heck, we're all excited! Not just the kids!
4. Tell them that for every 5 minutes they are unsettled after bedtime, they need to wait an extra 10 minutes in the morning before opening their presents.
5. Give them unlimited electronic time. At least it will keep them quiet.
Wendy suggested this list. I've done all 5 today.