I recently helped 3 women find their birth fathers, and one is building a wiki tree so this question came up. However we were lucky in the fact that both the sets of biological parents that were having affairs that created at least 2 children had passed on, so were just left with their children and grandchildren to deal with.
When I approached the living descendents, I searched on facebook for those that looked the "most well balanced", as the family seemed to have a chain of lives that would give the nurture/nature debate some great research material.
The families were in shock and a few "oh lordy, glad mama isn't around to hear this" were shared. However in the end, those families that are about love, acceptance and understand we are all humans having a human experience and understood forgiveness of things done long ago have no bearing on the human left behind that is simply researching for their roots.
I would strongly suggest though that there be no "online" ties to the family through "public" means unless they and their children if living are aware. However Grandchildren I don't really feel are quite as "important"
I agree it is important to document and each person has a right to their own roots, but in this day of social media many people unfortunately find out emotionally impactful things without the "human touch" which can have devastating impacts that might not be felt if one were to here the message from another human and have time to adjust.
You may be surprised at how open they are - if they are healthy, however in the end we are not responsible for other peoples reactions.. only our own actions.. and once they have had time to adjust, or if they don't respond to attempts to communicate, then I would say go ahead and publish.. even if they aren't "happy".. because everyone has a right to their biological roots..
And just as some people will defend the person who murdered his wife saying "my uncle wasn't a murderer, he got justifiable homicide and served 7 years take off that tag". The facts are the facts, and we have to present our history with those, which isn't always pretty.. some people want their families to resemble their "image" not necessarily the truth.
For me the truth is important.. as it is true humanity..