Dave's advice of watching out for silver diggers (the photo equivalent of "gold diggers") is good, I think. A lot depends on the practicality of scale, how the reproductions are used, and so forth. But, thinking about all that legal stuff in advance can't hurt.

As noted, too, the issues shift around a bit based on what you're reproducing from. If from the original negatives, the legal issues are far more clear. If you will be making copy negs of the old original prints, however, more research might be in order. You might also consider "crediting" the images to something like the "XYZ Family Archives" - just to make it painfully clear that you're not claiming personal credit.

the Barker kids, circa 1895. The young lad in the foreground was my grandfather.