What documents do I need to bring to extend my child's ED visa and my wife's O visa in Thailand?

Happy Sunday everyone .. I have a quick question as I'm planning to go to the immigration office with my child and wife tomorrow (Chaengwattana).

My 4 year old child is here on a ED visa and my wife has an O visa as accompanying parent. Both will expire (90 days) at the end of the month. I received extensive paperwork from the school on Friday. It's all in Thai but I assume it says he's still studying and we paid all the fees. So I'm not worried about that.

What else do I need to bring besides copy of passport / copy of stamped page / passport picture / birth certificate/ fee and filled out application? I didn't find too much on that topic. Does anyone have the same visa category and extended it already?

Thank you very much. I'm on my first tourist visa (60 + 30 days) and will get a new one in Myanmar next week (US passport). So that shouldn't be an issue.

Thank you very much for your help and time