Consider wearing (affordable!) hearing protection
Experts agree that extended exposure to noise over 85 decibels is dangerous. Wear hearing protection if the display will last a while or if you will be close to the fireworks, or if you have any doubts at all.
Fortunately, it doesn’t take much to protect your ears. Foam earplugs are cheap, simple and easily available from a pharmacy. They can reduce the levels of noise by up to 35 decibels, but check the instructions on the packet.