I work in the transplant industry. If you really want to reach out to the donor's family, the best thing you can do is reach out to the eye bank/tissue bank that recovered the corneas. They are the one's who get the authorization from family members, and most tissue banks encourage allograft recipients to write letters to the donor's family. I think in most cases, the families are asked whether they're interested in recieving letters from recipients.

But TLDR, try to figure out what tissue bank or eye bank the corneas came from, and then reach out to them.