If no one had been killed during he original raid, the ATF and FBI would have had more latitude. But, after 4 federal agents were killed in an ambush, while executing a lawful warrant, they had no choice but to lay siege. The parents chose to have their kids live with an apocalyptic preacher. Many of those parents chose to ambush and kill federal agents. Those parents chose to stay in the compound even as Koresh was making preparations for a Jim Jones end. Your assertion that the FBI killed those kids is an egregious example of begging the question. While I have zero doubt that you're not capable of being anything even remotely resembling objective regarding the events of April, 11th 1993 there is plenty of evidence that the FBI is not solely to blame for the fire.
Are you referring to the crime scene they bulldozed before anyone else could see it?