Populate repeater form programmatically

Hi All,

I am starting out on the custom module journey and I would like some pointers if possible.
I would like to populate the repeater list which is a form based on data pulled from a pages children, and I am not sure at which point to do this.
I was thinking of using a include directed to a file and looping to create the settings but that had issues with usability in the template area.
I am hoping the a repeater data has an accessible hook I could add to funtcion.php so I can access the data and add to it.