I feel for you!
Right now we live in front of a large lake. In our backyard is a deep ravine with tons of underbrush. There are at least 14 adult cats and too many kittens to count. They are very, very wild and won't let anyone near them, and we tried (with food, them getting to know us, etc). Anyways, the cats aren't really bothering anyone (they aren't on "our" property, and the city/gov't owns the lake) but it's so sad to see them out there. Especially the little tiny kittens.
We asked our vet about us keeping one or two of the kittens, and he said most feral cats end up having feline leukemia (AIDS) and it probably wouldn't be a good idea with our other pets.
*sighs*
Sorry I'm of no help. Just wanted to share.