If your son can tolerate kiwis:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9572406/#:~:text=Two%20gold%20kiwifruit%20daily%20are,considered%20as%20a%20treatment%20option.
There is data that kiwis can help move things along, again, if his body can tolerate it. I don't recommend depending on...