The American Chemical Society has a great page of fun Halloween based activities, demonstrations and experiments – you can find them at http://www.acs.org/content/acs/en/education/students/highschool/chemistryclubs/activities/chemclub-halloween-activities.html#P25_2879
But – remember that many of the activities need to be done under direct supervision of an adult or teacher. You can also find – safety tips and resources on the ACS pages or from Sophic Pursuits