Naturalistic driving studies have shown that pediatric occupants do not assume ideal seating positions in real-world scenarios. Current vehicle assessment programs and child restraint system (CRS) sled tests, such as FMVSS No. 213, do not account for a wide range of seating postures that are typically observed during real-world trips. Therefore, this study aims to analyze the kinematic and kinetic response of a pediatric human body model in various naturalistic seating positions in booster seats when subjected to a frontal offset impact in a full-vehicle environment, with and without the application of pre-crash automatic emergency braking (AEB). A 6YO (seated on a lowback and highback booster) and a 10YO (seated in no-CRS and on a lowback booster) PIPER pediatric human body model's response was explored in a reference, and two most commonly observed seating postures: forward-leaning and forward-inboard-leaning. The vehicle environment with a side-curtain airbag (SCAB) was subjected to a small offset barrier impact (25% overlap at 40MPH), with and without the application of a pre-crash automatic emergency braking (AEB). 24 conditions were simulated using finite element analysis. Cases with a pre-crash AEB resulted in relatively lower kinematic and kinetic values due to the occupant being in a more flexed position before impact compared to without-AEB cases, coupled with the increased ride-down effect due to AEB. Moreover, different seating postures resulted in substantially different kinematics and kinetics, the injury metrics crossing the injury assessment reference values in some cases. Therefore, to design a passive safety standard test for pediatric occupants, it is important to consider the possible postural changes that may occur.