first of all...toxicity of any vitamin is something that has not occured in this population in years. it is next to impossible to "overdose" on vitamins.
when a cereal is 'fortified' it means that all of the vitamins removed during the refining process are added back in....primarily B vitamins. cereals with whole grains have fiber in them. 25-30mg/day is a healthy dose of fiber. (just because a cereal contains fiber does not mean it is 'only for adults').
KIDS NEED MORE FIBER/VITAMINS/MINERALS