Disallowing vampire characters makes sense (they're hated for good reason), and they should already know that the Golden Willow is off-limits for them when they turn. But prohibiting someone playing a human character who happens to be a minor, that's just unfair to the players using them.
Also, having children in the tavern doesn't kill RP. Their skins may possibly be a distraction, but I've seen plenty of adult characters with eye-catching skins as well. You simply choose to pretend they aren't there, and move on.