I think this is a wonderful thing you are doing. Feral cats are a real problem where I live, and I can't believe with all the publicity that people are so irresponsible as to dump unwanted kittens. There are cat havens here where cats can be sterilised for next to nothing, and still people don't do it.
Good for you. I hope you get joy out of knowing you've helped defenceless animals have a better life.