If she can find him, he can find her. So that begs the question, does she want to be the one to tell him ... or does she want him to find out on his own?
I have an in-law that handled it this way. She contacted a local attorney in the city where her children were located. She authorized that attorney to provide her contact details if the children requested. She then had the attorney contact the children and inform them that he was in contact with their mother, that their mother was willing to reestablish contact if the children wanted to do so. No further information was provided.
The children were contacted, and it took a few months, but they eventually requested her information. After some back and fourth via letters, that led to a phone call and eventually to a visit.
He can’t find her because she did not give up her DNA.
I don’t really know much about this other than what I posted, but I found it interesting that a sister giving up her DNA found a match. Oh, I just remembered that her sister put a “hold” on giving out her DNA info so he would not see it.