I hadn't known that kombucha tea was slightly alcoholic, but if you say it is, or can be, I'm not surprised. But I wouldn't sweat it. We just don't live in that kind of world: the kind, that is, where you can always get zero of x (whatever x might be). I think that if there's any alcohol in there it's not going to amount to much. If you wanted alcohol, you'd have to use a good quality strain of yeast, not a kombucha fungus. If there's some alcohol in there -- a fraction of a percent or whatever -- it'd be no more than what you'd get in fruit juice if you left it around for a day or so after pressing it before drinking it. And if there were some alcohol in there and you waited a bit longer it would probably get converted to acetic acid (vinegar) -- unless you had some way of excluding bacteria that would do that ... not easy in an open vessel in a domestic situation.
Yeah, it could be a good idea to avoid booze -- for example, if one never knew when to stop once started, but making avoidance into a fetish just isn't necessary. As I say, we just don't live in that sort of world -- heck, some people can be over the limit of a breathalyzer without drinking on account their own bodies make alcohol.