Thanks for your great answers! For the safety of my own family, I've already invested in the removal of all lead problems from the house. A final comprehensive inspection would be a relatively minor cost (several hundred dollars) compared with the original work. Offering to pay for the inspection if the interested family has young children sounds like good idea.
I'm wondering whether buyers would generally be much influenced by a lead-safe or lead-free certification. I think that I would have been, but I didn't notice a certification for any of the houses that we considered when we were buying.
For example, "14 Hudson Pl, Cranston RI" shows as "for sale" in Zillow, but is not actually for sale.