Don't invite child over before 5pm.
Hide all random sweets/chocolates/beauty products/dresses/shoes/cameras/computers
Rent a very long DVD
Put them to bed and give them half an hour of legal chat
Be ready for the inevitable, "I feel sick, I need a glass of water"
Give them a glass of water.
Make sure partner is in
Keep a night light on (One eight year old girl peed in my daughter's play box in the middle of the night because she said it was too dark to find the door)
Take it in turns to go upstairs and say shhssss/be quiet/this is the last sleepover before Christmas.
Very important: Wear ear plugs when you go to bed because they will get up and make noise at 5 or 6 a.m
Send a cheery text when mother of child texts to ask if everything OK
Be prepared for a very overtired, overwrought, child for the following 2 days.