Donna,
There will always be quite a few dogs in every breed in rescue that cannot be safely rehomed with children/cats. Sometimes it's just precautionary and sometimes there is evidence that the dog is unsafe around them.
But it IS possible to get rescue cockers that get along well with children and cats. Myself, Beanoandcharliesmum and sallyjack all have young children and rescue cockers.
When I took Toby on, he had already lived with children and been child-tested by the rescue but he had never met a cat. This hasn't been a problem for us as, after an initial barking match, they have settled down together well.
It's often a matter of waiting patiently for the right dog to come along. I'd almost given up on the idea of finding a cocker when Toby appeared on the Irish site. I had contacted cocker spaniel rescue but they had told me they would only rehome where there were older children. This shouldn't be a problem for you. Is your name down on the breed rescue list?