I also don't think guests really are obligated to keep track of credits to ensure they don't violate this rule. The only thing I believe guests are obligated to do is to not plan to violate this rule. Even more specifically, it means not paying OOP for children, with an eye towards using those credits for adults. It means a family of two adults and two children shouldn't be sitting together at a quick service table with three adult meals obtained with Dining Plan credits. That sort of thing.