Personally, I think it depends on the atmoshphere one is in. But all in all, NO ONE should be getting to a point where they are too sick. It just looks unappealing and probably not what the chachamim had in mind. If the underaged kids are in an atmosphere where the seuda is totaly focused on growing in torah, yoddishkeit, middos etc, and there is a rebbe (and rebbetzin) there that have control of the situation, than it shouldn’t be a problem (because the problem won’t exist). If one is in a situation where there is total hefkairus, than under-aged kids should not be drinking. For example, in Israel, when you’re by your rebbe’s seuda, things don’t get out of hand too often. However, when in America and the seuda is with friends, it’s more of a recipe for nisht pashut times, especially if the kids there are going in with the mindset (kavana) that they are going to get smashed and do stupid, immature things.
Purim is supposed to be a holy and special time, DONT SPEND IT IN THE HOSPITAL (C’V) OR LOOKING REALLY SICK! ENJOY IT RESPONSIBLY AND BE BE’SIMCHA (you can’t be be’simcha when you’re too sick). SHOW THE WORLD WHY WE WERE SAVED AND WHY WE SHOULD BE BE’SIMCHA!