Turn present opening time into a fun game of its own
Liz's house sounds like a merry place to be on Christmas morning:
My family has a fun tradition for Christmas gift-opening. When the family gathers around the tree to open gifts, everyone takes turns opening gifts rather than diving in all at once. This isn't so unusual, but we add a twist: Before opening a gift, the recipient must try to guess what's in it!
This leads to all kinds of trickery on the giver's part. I've seen gifts double-wrapped with bricks, a pair of earrings taped to the lid of a refrigerator box, clever notes and poems describing large items tucked into wee jewelery boxes, and an entire roll of quarters taped loosely to the top of boxes to make odd noises when the box was shaken. (That was also a bonus gift, as the recipient was collecting bicentennial quarters.) Kids as young as 6 or 7 can be encouraged to participate (start them with a toy that they can play with while they're waiting for their turn to come around again) -- it helps stretch out the fun of the gift-opening phase of Christmas morning and teaches kids about the enjoyment of anticipation.
Related: Lots of good holiday hacks in the Holidays/Special Occasions archive.