My dogs look for birds dropping that they need to retrieve!
All my dogs, including non hunting dogs are trained to not be noise shy. You can read up on it - generally start immediately when they come home as a pup - banging around during feeding times, then play times with increasing noise level, so the dog learns that bangs are good or at least nothing to worry about.
My old dog can't hear much anymore. I estimate 5000 rounds going off over her head in her 13 years of life. My younger one perks up when there is a shot or fireworks, hoping we join in!
I am sorry for the dogs who are firework / gun shy. I would try to work with them every day to see if it can't be dampened, much like you work a pup. Most old dogs do learn new tricks. The key would be to step it up extremely slowly not to make matters worse. Work on it every day of the year, not just in July.
Good Luck tomorrow you pooches and owners!