Here "children" is a metaphor for being spiritually immature. Alternate translation: "when we were like children" (See: [[rc://en/ta/man/translate/figs-metaphor]])
Here "enslaved" is a metaphor for being unable to stop one's self from doing something. This can be stated in active form. Alternate translation: "the elemental principles of the world controlled us" or "we had to obey the elemental principles of the world as if we were slaves" (See: [[rc://en/ta/man/translate/figs-metaphor]] and [[rc://en/ta/man/translate/figs-activepassive]])
These words could refer to 1) the laws or moral principles of the world, or 2) spiritual powers that some people thought control what happens on earth.