Sorry to chime in late, but have you tried contacting any local genealogical societies or local history societies in the areas where you know these folks lived? Sometime you will hit a real gold mine through sources like that (or not!) What you might get that way would be obituaries or birth notices, not otherwise preserved, cemetery listings, and sometimes marriage notices.
I would also suggest that you try the GenWeb site for each county where you know people were, for the same reasons (that's really hit/miss, but sometimes you can get great stuff that way).
Also, I would do a name search on Find A Grave for the counties where you think the family might have been. This will give you a list of cemeteries (as you mention) and if they are reasonably well documented, you may be lucky enough to find a memorial - and if it has a photo of the gravestone, that's an important bit of information. Even if there is no photo of a gravestone, however, the person who created the memorial may be able to tell you where the information came from, and you then can check with that source (e.g., may have been from the cemetery district, may have been from funeral home records for that county, or who knows what).
Good luck with your search.