Is it ok for my kid to chew or swallow his halloween candy/gum without brushing teeth?

No. Normally teeth need to be brushed in the morning and prior to bed time. If your child is chowing down on candy then they should brush an extra time. Anytime food (especially sweet sticky food) is left on the teeth it promotes tooth decay.
Brush After Sugars. It is important to brush, or at least rinse with water, after eating sweets. Then most of the sugar & food particles are washed away & do not fead billions of bacteria that normally live in the mouth. While not known to be harmful, chewing gum should be spit out & not swallowed. Chewing gum while laying down can be dangerous if it goes to the back of throat & is inhaled into the lungs or windpipe.