Keep tonight safe and fun for everyone. Have your pet stay in a room away from the hustle and bustle. Prevent accidental escapes out of the open door, and negative interactions with ghosts and ghouls. Keep candy and treats in cupboards or on the back of counters where "counter surfers" can't reach them.
Monitor costumes and small pieces that may fall off or be pulled / tugged by cats and dogs. Even a string or small piece of fabric can become a major concern if ingested.
If you have any concerns, reach out to your veterinarian or an emergency facility immediately. Have a safe and fun Halloween!