What constitutes a child soldier is clear and Khadr did not meet it according to the UN. He pled guilty to terrorism, and having blood on his hands, and showed remorse to his victim's widow and her children. One does not fake an apology of this magnitude, no matter the fateful outcome, as it reflects being a liar trying to avoid being hurt. Being contemptible.
Omar Did have grit facing an Alamo situation. He nearly died in a hail of bullets, presumably not wanting to live. He was part of al qaeda, the group that caused 9-11 and brief financial uphaeval- his father being in the thick of it.  A family committed and within the circle of bin laden. No getting around him building, and planting IEDs in the dark of night.  Khadr was a prince, born, raised, trained, in the culture of al qaeda, an organization devoid of humanity. He lived this nearly 16 years, 10 years imprisoned, around 4 years guard and about  3 years as a Canadian. This was not a poor child soldier from a peasant village.