Well the entire point of having super acidic stomach juice is to kill of microbes, so whatever you eat is disinfected by your stomach. And even if some microbes from “probiotics” reach your gut… they still have to deal with the microbes that are already there.
So just keep eating healthy and you’ll be fine. 
And at the event it’s probably best just to eat packaged food or well heated food if you want to avoid stomach issues.