Is there an area close by where they are eating now that you could set up a feeding station, away from the house, but near where they're use to being? Relocating has steps to follow in order to have the cats stay in that location. Could you relocate them to your place with a feeding/watering station? Have you contacted anyone from Alley Cat Allies?
http://www.alleycat.org/
They may know of someone in your area that would be able to help you. It would be a shame to have these cats destroyed after years of feeding and they're all fixed and not reproducing! Please check some of the feral cat rescue sites out, they may have suggestions for you!
Trap-Neuter-Return (TNR) is a full management plan in which stray and feral cats already living outdoors in cities, towns, and rural areas are humanely trapped, then evaluated, vaccinated, and sterilized by veterinarians. Kittens and tame cats are adopted into good homes. Healthy adult cats too wild to be adopted are returned to their familiar habitat under the lifelong care of volunteers
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