Ditto, Ginger! Traditionally, the elves visit the 12 days before Christmas...but you can have them visit as long as you want. They have to be still during the day, but at night they're adventuresome. You could say that they're Parent Powered! As Ginger said, you can do as much or as little as you want - but I've found that the more you put into it, the more you get out of it. Watching the morning reactions is priceless, magical, heartwarming, ...
I love the
Elfing Around program. They give you the elf and all the adventure ideas and supplies you need. They also have downloadable freebies. Hope this helps!