I get plenty of private mail so I don't know what happened to Brent's.
I really don't want to get too far afield, and I appreciate all the tips and pointers from those who did answer my question helpfully. I won't have the bandwidth to offer many more answers. But there is one comment to be made.
Brent's "help" hasn't hasn't been helpful at all, and I am replying publicly because there are lessons within. I asked for assistance with A and get in return volunteer advice on B; that seems to happen often in Linux forums. But in this case, the advice was grounded in assumptions (ie, about crime and vandalism) that are baseless and borderline racist.
Refugee settlements are not ethnic ghettos. They mix colours, tribes and religions, generally in peace. What their residents share, for the most part, is having been through absolute hell; for some of them the choice was "live in a community or die alone". They have every reason to be bitter, angry or resigned, but those I met were none of that.
That's not to say all is well. There was a hanging one morning during the time I was at the settlement; the victim was identified as a spy for a government that people were running away from, and not a resident of the settlement. I saw the body after it was cut down; I was told this was not a common occurrence.
Nothing that I or any other do-gooder helper can do is going to eliminate THAT kind of conflict through rich-world "community building" exercises. Based on what I saw, people running away from atrocity can sometimes teach us more about community and cohesion and sharing than we could ever teach them. (I heard the word "Ubuntu" used in context that had nothing to do with Linux.)
So... if you didn't have advice for what I asked, that's cool, it was a fairly specialized request. But please, think twice before using the request to indulge in gratuitous "why don't we just...." commentary. It's an unhelpful distraction that betrays bias more than it offers help.