To the best of my knowledge, MIMIC-III only contains data pertaining to adults (or adolescents treated medically as adults). There are a few records of neonates from childbirths, but it is not the main focus of the database.
If you run this:
SELECT * from
SELECT ie.subject_id, ie.hadm_id, ie.icustay_id,
ROUND((cast(ie.intime as date) - cast(pat.dob as date))/365.242, 2) AS age
FROM mimiciii.icustays ie
INNER JOIN mimiciii.patients pat
ON ie.subject_id = pat.subject_id
WHERE ie.DBSOURCE = 'metavision'
) as A
WHERE age < 16
you will get 3 results, such as
subject_id hadm_id icustay_id intime outtime age
32035 113114 269627 2159-02-15 21:01:05 2159-02-16 19:16:36 15.05
These are ALL the subjects under 16 years of age whose data was collected using the Metavision system. If you include the CareVue system, you will get 9 results in total.