Don't we say that every baby is a muslim at birth, just diverted by parents/society etc to other religions or atheism? Therefore, if an orphan was once a muslim and has been led astray unknowingly, I wouldn't regard them as 'children of kaafir' until they make their own choice at a later stage.
by the way if you are looking to feed the poor and you want to do it physically yourself as opposed to just sending money abroad or whatever, and if there turns out to be no muslim organisation in your area you can work with, then I would encourage you to just take a walk some evening down a street in london or your town and if you see a homeless person or a begging person stop and ask them if you can get them something hot to eat.
In my experience it's appreciated by any human soul as most of them are sitting in the cold for hours.