Nothing is guaranteed safe 100% but it will definitely make you safer. Make sure your musicians ear plugs are at least -20db. A guy on this site went to a concert with -11db plugs and made his worse because it doesn't reduce it enough to not damage. -20db should at least get you into the 80s DB level which is a lot safe than the 90s. Stay away from the speaker and go take a breather after 30 or 40 minutes for 10 minutes (hit the washroom grab a drink) to rest your ears for a bit to be extra safe. I'd also recommend taking N-acetyl cisteine and Magnesium starting from a few days before and for a week after, it has been scientifically proven to prevent hearing damage from loud sounds in soldiers and clubber. You can pick up a bottle of each for probably under 40 bucks for both I think.