Longtime nurse here.

I'm not an expert in microphones, but I do disinfect things. I would recommend using wipes, so as not to get any disinfectant inside the microphone. Quick-drying products would be best. Something like these:

https://www.amazon.com/PhoneFresh-Disinfecting-Screen-Pre-Moistened-Cleansing/dp/B07J3KKT82

You could also have a bottle of hand sanitizer for people to use before they go onstage.

BTW, ANTISEPTICS are intended for use on people. DISINFECTANTS are intended for use on things, and may be too irritating to use on people.