On Christmas Eve after the children are asleep in bed, Santa shows up (scheduled between 10:00 PM and 2:00 AM). He'll deliver the gifts right in front of their eyes!
This is a wonderful way to keep the magic of Christmas and Santa alive. Especially if the children are getting to that age where they're starting to not believe in Santa any longer.
You'll wake the children "Hey! Santa's downstairs! Let's go see!" and you all watch Santa put the presents out, eat the cookies, drink the milk, and other fun stuff. Remind the children to be quiet, you don't want Santa to catch you all spying on him! Just before Santa's done (and Santa's code word to the parents) you'll rush the children back to bed so Santa can make a hasty retreat! The children will remember this for a lifetime!
The "event" itself is typically less than thirty minutes total from start to finish. That includes arriving, getting the presents from the parents, and getting in place before the children are woken by the parents. Then they all watch Santa for about ten minutes at the most before the children are rushed back to bed and Santa makes his exit.