For all the risk of unending drama, who benefits in what way?
I get the impression its more for her kids (knowing they have more family, aunts and uncles) than for herself. Although, I'm sure curiosity plays a big part in it as well.
A couple people did mention the father didn't respond for a reason, I think that is still unclear. A letter was sent but no reply received, it's presumed (hoped?) it made it to the right person. On that end I told her to send another and let him know she wanted to reach the children. I think she presumed the no response was intentional, but I tend to think you should at least try twice to be sure.
Gotta be weird for that guy tho, from the biological mother, she broke up with him when she found out she was pregnant. Never told him, he want off to Vietnam. They never spoke again. I tend to wonder if he even believed the letter 'Dear so and so, remember dating this lady almost 4 decades ago, well guess what....' That has to be kinda, well strange (but as I guy I figure its better than finding out before they turn 18
)