Seeing as all parties involved live in Cuba, it is in fact quite possible that some editing was done for political reasons. Seeing as his widow and daughter were involved, it is also quite possible that some details were altered (or even removed) to avoid bringing any embarrassment to the family, or that might tarnish his memory in some way.
Some editing of content was certainly done. His daughter admitted as much in a 2004 interview (translated to English here):
Since the 1980's, we - Che's family and others - have been working on
his unpublished manuscripts. These were maintained as part of his
personal archive, and in large part were and continue to be jealously
guarded by my mother. To publish anything written by him that he
himself did not intend for publication - as is the case with the notes
that became "The Motorcycle Diaries" - serious editing work is
required. We can't omit text, but at the same time we can't be
completely sure he would have given his permission for the text to be
published as it was originally written. That is why we have a
commitment to edit what he wrote without changing what he meant - a
very difficult task.
Perhaps sometime in the future when all his contemporaries are deceased, the unedited diaries will be allowed to pass into the care of some group that will allow outside historians access to them.