One of the primary official motivations in terms of the entire conquest (taking a step back from individual desires of wealth and prosperity) was the Catholiciz

One of the primary official motivations in terms of the entire conquest (taking a step back from individual desires of wealth and prosperity) was the Catholicization of the settled lands. The Conquistadors as a whole were people. People can be good, people can be shitty. And the same can certainly be said for any potential aliens. But I am not aware of any official campaign which included slaughtering children, or anyone else for that matter. In fact, one of the earliest laws drafted (https://en.wikipedia.org/wiki/Laws_of_Burgos https://en.wikipedia.org/wiki/Laws_of_Burgos) includes an explicit article forbidding it and other forms of maltreatment: > 24: The Indians are not to be physically or verbally abused for any reason. And the laws were even expanded to further protect women and children.