I've been tossing around the idea of running a short adventure set about ten years before the events of The Worldwound Incursion happen. I was thinking of having each character no matter what race create a child that's at least ten years or so younger than adulthood and run some stuff that helps set up the major NPC and factions of the city that from what I can tell aren't all that well established if the players aren't already familiar with them to begin with and take the time to explain them in the heat of all that happens in the midst of the destroyed city.
I'm here to pilfer ideas from people to see what could be fun but also help set up a connection for the players to really care about what happens to not only the city but also its people.
I've written a small session (1/2-1 sessions long) that I'm calling the prologue. My players are choosing to travel to Kenabres for the festival instead of being born there, so I'm going to be running some rp encounters and a few low cr battles to get them situated in the city. I have them arriving about a week before so they can check out the city and get to know some people around and relax.
I hope that helps in some way!
Although I do not have a lot you can pilfer from me. However it should be rather easy to get some simple quests going. You have the whole article about the city before it gets torched. factions and what they do regularly are very well described in other sourcebooks.
I would (like I have a tendency to do) be the voice of caution. Having all players have a child might be forcing a backstory on them that they don't want. Some of the background traits rely on those parents. others would make more sense if that wasn't the case at all. forcing it seems a bit restricting on your players.
I would also caution against making this prequel (to) interesting. the AP is going to end with the heroes accomplishing one of the most legendary feats in the world. if at any point the players feel that the prequel was more interesting, and they want to play that, rather then the AP. it fails as a prequel (although you might have more fun that way, not for me to judge).