Most people have pulled off (or know someone who has) the old underage bar trick of getting a non-alcoholic drink from one bartender and asking another to top up their "drink" with a little more alcohol. The unaware bartender thinks that straight orange juice is really supposed to have more vodka in it, and voila -- the underage person has some alcohol.
Bartenders know that alcoholic and nonalcoholic drinks need to be separate, both for legal and health or religious reasons, and they know that they need to not fall for those tricks. Yet in a busy restaurant, it can be difficult to memorize who had what. The glassware you use in your restaurant can help.
Why Charms and Wristbands Aren't the Answer
Many all-ages venues use handstamps or wristbands to visually distinguish who is allowed to have alcohol. However, those aren't good methods for two reasons. One, they go by age, so someone who simply doesn't want alcohol might mistakenly end up with an alcoholic refill if they aren't careful. Two, those don't prevent someone over the drinking age from getting an alcoholic drink for someone under the drinking age. Glass charms aren't the answer, either, as they can be lost, broken, or swapped.
Glass Texture, Color, and Shape
With glasses, differences in texture, color, and shape can be visual cues regarding what's supposed to go in the glass. For example, a clear wine glass could be for people who have ordered (and whose ID was checked) wine, while a blue wine glass could be for people who have ordered a nonalcoholic drink. Yes, it's still possible for someone to order a new drink and pass it to someone else, but no one can grab someone's glass and surreptitiously sneak them some alcohol because the bartenders will know that no alcohol is supposed to be in that glass.
Keeping It Subtle
Any differences in the glasses should be subtle. You don't want to make non-alcohol drinkers feel called out. For example, maybe you have clear glasses that all have decorative streaks on them, with one type being red or yellow and the other type being green or blue. Classy glassware can go a long way toward making everyone feel welcome at your restaurant.
Your glassware and other glass products can help you run your establishment more smoothly. Take a look at glass catalogs to see what distinctive glassware you might like. Contact a libby glass supplier for more help.