"No grandfather paradox because it is only data with the potential to be formed into images that is out there not the material past."
Unlike the twin paradox, the grandfather paradox is a true paradox of relativity.
It does not depend, as you imply, on the observer's ability to see what is "really" there. It is the single case that implies the general case;* i.e., if travel into the past is possible, any change in the trajectory of events alters the outcome, such that the metric backward is asymmetric to the metric forward. However, knowing this is equivalent to being able to change the outcome such that symmetry is restored.
In the case of the twin paradox, the outcome is entirely symmetric; the future-traveling twin is actually younger than the stay at home twin, because time actually goes slower for the traveling twin in proportion to the distance traveled. No paradox. In the case of a single being traveling into the past, there is no point of comparison -- it is all based on self-interaction. In other words, the twins have a specific reference point (though neither is a privileged 'reality') while the grandfather-killing individual can only reference herself in relation to every event on the trajectory into the past -- such that if every relation is constant up to the critical event (the killing), that critical event creates a new trajectory orthogonal to the original. (Of course, while an infinity of critical events is possible, we are only interested in one.)
The grandfather paradox therefore differs from the twin case, in that it depends on a discrete (quantum) event, while the twin case is purely classical (continuous).
Now compare the grandfather paradox to the phenomenon of quantum discord I referenced earlier. If my conjecture ("For every classical measurement, there exists at least one quantum state") is proved as a theorem, the discrete state is continuous with the historical trajectory; no quantum entanglement, no nonlocality, no grandfather paradox. A time traveler into the past indeed has the choice to act, or not -- because there is no boundary between quantum and classical domains. Cooperation among least elements in any system at every scale is driven by the essential metaphysical property of free will.
* An analogous example in computer science is the P = NP? question. It is formulated such that if one problem considered to be NP complete is found to be in P, every problem in that class is in P.
