It’s true that choices involving privacy, in particular, are very hard to reverse. Once those other biological half siblings and their parents know she is there, your daughter can’t very easily disappear from their awareness. But the opposite choice will have consequences that are hard to reverse, too: Because growing up in touch with someone often establishes a very special kind of relationship, not growing up in touch with someone deprives you permanently of that experience. Yes, these ties are optional, in a way that’s not obviously the case with nondonor kinspeople, while perhaps fraught with the expectations that can come of shared ancestry. But, as with your other relatives, there’s no way to know in advance whether these ties will prove rewarding and welcome. And the maxim “better safe than sorry” provides little guidance. It’s no use deciding to err on the side of safety when it’s utterly unclear which side that is.
We’re sometimes too preoccupied nowadays with the question of epistemic privacy — with preventing others from having access to facts about us. Plenty of people will inevitably end up knowing plenty about your daughter as she grows up; her kindergarten teacher, her schoolmates and their parents will certainly know just the sorts of facts that you might be contemplating sharing with her biological half siblings. You ask about the ethics of sharing “her identity and some personal information.” But what — aside from the fact that she is the child of a sperm donor — does that really mean? Her name, her age, the state where she resides? How does someone knowing those things pose a threat to her that she might reasonably complain about later?
And remember, while your child remains young, you’ll be determining not just these contacts but all her contacts. She will have play dates with other children only if you permit it. So one test for passing on information is: Would I tell this to the parent of a child whom my child was going to go on regular play dates with?
You mention one other consideration in passing: These contacts might help you in your life as a single mother. This interest, you seem to suggest, might be in conflict with what’s in your daughter’s interests. But having a flourishing mother is going to be in her interest, too. You’re right to give these issues serious consideration. As a general rule, however, the well-being of parents is aligned with the well-being of their children.
My son was temporarily laid off from his job in April, within a few weeks of starting. His employer helped him and his co-workers sign up for unemployment benefits, and he started receiving those checks within a few weeks. He lives in a rental apartment alone, so like most of us, he has bills to pay, but he has always been very careful with his finances and has money saved for a rainy day. For a 25-year-old, he is doing OK financially.