The SPCA website outlines some things to consider for your pets during trick or treating and fireworks. Strange looking people in costumes can cause friendly animals to feel threatened and become aggressive. Running from loud noises is a typical response for many pets.
Keep in mind that fireworks might continue for the days following Halloween; it seems if people get their hands on fireworks, they must set them all off!
If using fireworks, please also consider wildlife. Startled birds will collide with trees, cars, and buildings. Wildlife and farm animals become tangled in fences as they flee the loud and unusual noises.