This question assumes that the shades Harry saw in the Forbidden Forest were really part of the souls of his parents, Lupin and Sirius and that they could think for themselves - which I believe is the point intended and a concensus reached on this site via other questions. (Practical value of the Resurrection Stone and Why didn't the resurrection stone 'work'? for example).
Assuming this is true, is there any evidence to clairify if they believed that they were genuinely supporting Harry in his approach to death or if they were somehow aware of Dumbledore's big picture?
What I mean is, could they share a secret comfort that all would be well, or at that moment did they believe they were shepherding their son/close friend to be murdered by an evil, frightening enemy? I know that if this latter idea was true, the messages are that they have learned that death isn't such a bad thing after all and that his sacrifice (like their own) would be so valuable to the world... but how hard for them to think they were sending their own son to die at the hands of a murderer at 17.
I am asking if there is evidence from the books or JK Rowling - not merely for opinions. I hope that I have successfully taken these thoughts and boiled them down to one question successfully.
Edit: The suggested question is extremely close to mine, and if I had found it when I searched I mIght simply have accepted the answer because that answer addresses the bulk of my question even though the question was different (as often happens). However, in writing my question and looking at comments on it, I am still interested to know if it is possible that Harry's family and friends could have known that he would not truly die.