Taiwan nationality for older mixed blood child?

I’m a newbie at the site, so apologies if this has been answered before.

I’m Canadian, my wife is Taiwanese.
My three sons were born here in Taiwan (1993, 1994, 1995) before the new dual nationality laws, so had to have ARCs.

I carelessly let my oldest son’s ARC expire (this year, long after the new law.) The two younger had three-year ARCs which expire next month.

Is that a problem for the oldest?

How do I register them as RoC citizens?
I was told by a friend in the same position that I have to take them to the Immigration Office in Hualien or Kaohsiung ( I live in Taitung,my kids were born here, household register is here)

If they were under the age of 20 on Feb. 9th, 2000, or born after that date, and have at least one Taiwanese parent, you should visit the local Household Registration Office (HRO) to get them registered as ROC citizens.

However, you have to be aware that the law does not always apply uniformly, depending on where the children were born . . . . . . . so you need to ask the HRO people about it.

Okay, have been told at HRO that for a child born in Taiwan but before the new law passed you have to supply pictures, passport and ARC as well as birth certificate.

I’ll go in Monday and see if oldest kid slips under the radar with expired ARC.