Well... do you have better advice? Going to the cops would be an obvious alternative, save for the fact that they have no obligation for confidentiality. Plus, depending on the details of the blackmailing and where all this is happening, local cops might not have jurisdiction.
Given the apparent sensitivity of the photos to which OP alludes, I would hope that an attorney would be able to minimize the damage while addressing the crime being committed (if indeed that's what's going on).
I hope we hear back from OP with more about what's happening and what he is doing about it.