Dear ..........?
Maybe it �s an idea to decorate slices of cake? Your pupils could form a Halloween face on the slice (eyes, nose, mouth, hair) with sweeties and raisins or vegetables as carrot, apple, paprika etc. Hair could be made of liquorice (if you know this sweet in Japan). All stuf could be sticked or glued together by means of sweet frosting.
Here in Holland we have little, coloured chocolate rounds. They are very tasty and often used for such activities.
Hoping being helpful to you.
Lots of success and pleasure!!
Best wishes from Holland!
(Perhaps you will be able to answer me when this is a useful hint?)
Ans Kwak