I can't say that I have any advice, but I would make sure your cats are current on FVRCP, FIV/FeLV, and rabies vaccines. That is pretty bad exposure to the worst diseases.
Most of us here condone 'indoor only' cats, and I know that's 'easier said than done' when you got cats accustomed to going outside.

There is a product, a spray, I believe, that deters animals from coming close.
It may effect your cats too, however.

Sorry about your situation.