The laws regarding the age for drinking wine apply to all, EXCEPT for the single kos yayin that is required for religious observance. Our government recognizes that sacramental wine is necessary for Shabbos and yom tov, and no one tells parents not to give them wine for kiddush, though one may be yotzai on grape juice. My parents always watered down the wine my father O”H served to the children, until we were of an age to tolerate the undiluted wine. He always mixed our wine half and half with grape juice on Pesach (because otherwise, we fell asleep before we got to Shulchan Orech). Ben Levi’s point is incorrect. ALL other wine drinking except for Shabbos and yom tov kiddush, is assur under age 21. But no frum Jew will be arrested for serving wine at kiddush for those who are underage. And MORE IMPORTANT — those underage people who are drinking wine at Shabbos or Yom Tov Kiddush, ARE NOT GETTING BEHIND THE WHEELS OF A CAR until that alcohol has already left their systems. And that makes all the difference in the world.
