Probably a bit late for this year, but in the hope that it helps those who have dogs that are very frightened, this is what worked for my first 2 dogs, who were very scared:
kept them hungry (small dinner previous night, no breakfast), then gave them a big meal with lots of carbs (pasta, rice) around 5pm, which seemed to help make them a bit sleepy
gave them very long walks to tire them out during the day
Australian Bush Flower mist, emergency formula, sprayed on to a bandanna, tied (loosely!) round the dog's neck, so the smell is right under their noses
phosphorus 200c from a homeopathic vet
melatonin 100mg, with their meal
That little lot made it tolerable for them on 5th itself. Thundershirts, DAP diffusers and desensitisation CDs made no difference whatsoever.
Of course, it's no use for random local displays that take place without warning, or when a fireworks factory catches fire, which happened a few miles from me about 12 years ago.
Current dog isn't that scared (she is a very bold little dog), but she barks at them, which drives us mad. We now go out to a very rural pub, have a meal, and spend the night in their car park in our motorhome. Although we can hear the big displays (which are 8 miles away), they're not near enough to bother her. Or us, which is good as as they go off intermittently till around 3 am, and sometimes beyond.