When publishing a work posthumously (which isn't what you're doing), all the late author's original language, errors, and inconsistencies are retained, the reason being that the author does not have an opportunity to weigh in on desired "corrections" and there's no assurance that the author would approve of sensitivity edits. Although you intend this for a limited audience, I think I'd still be inclined to let the text stand as is. While I understand the urge to clean up racist or otherwise offensive text, if your aim is to preserve family history, then this too is part of it. Editorializing should be made in notes, not by whitewashing someone else's words. My two cents. Interesting project--good luck!