What measures and pitfall should I consider when running an especially unstructured narrative in Pathfinder?
In the campaign I am running that has started recently, I am attempting to run a fairly "open" story that avoids blatant railroading. While I wish to present the characters with problems and challenges to deal with, I do not want to strongly guide them toward solutions; rather, I want them to be proactive in coming up with their own creative solutions. I want to provide the stimuli, but I want to avoid dictating their reactions as much as possible.
However, I am not sure if it is problematic narratively, to what extent, or how to best compensate. In the typical D&D structure that I'm used to, the group would have relative confidence over what their current "quest" and goal is, when they can (and "should") rest, and what kind of overall encounter difficulty to expect in an "adventuring day". My plan for GMing throws out most of these expectations.
As an example, the game thus far began with the PCs' shared hometown being attacked by monsters (and successfully defended by them). The details of this attack are largely unknown and mysterious, leaving the players and characters left with uncertainty.
Based on what I know of the players, they will deal with this issue with intelligence and planning, but possibly to the point of paranoia. Since they don't know if they drove off all the attackers or when more will be back, their characters might be always on edge for hours or days following. Since the attack happened in the middle of the night, they may be afraid to sleep, or their sleep schedules might get out of whack. They might become frugal with their spells and resources "just in case" something else happens at any given time. They might avoid taking risky avenues of approaching the situation (such as exploring the nearby countryside for clues) in favor of safer, cautious options (fortifying town defenses and waiting until another attack happens).
Personally, I find this kind of on-edge paranoia over mysterious circumstances to be interesting. It is probably a fairly accurate and realistic model of how a small town of people might react to a sudden and unexpected disaster. However, realism doesn't always make for a good story. Should I be concerned about this possibility of paranoia and overly cautious behavior? What are good ways to help this go smoothly?