Maybe they are already too old for this but it's fun and fits the season: paper stars
You take a square sheet of paper and fold it into a triangle. Then you fold it again and again, as often as you like. Then with a pair of scissors you cut little bits out of the folded edges or from the tips. When you unfold it, you have a pretty star. These stars make lovely tree ornaments or can be stuck to the window.
Instead of normal paper you can also use metal foil or (round or square) paper doilies
These links are in German, but the images will give you some ideas