Hoover, I so agree with you about some dogs are born with a difficult temperament . Bob was like it from day one. His problems with eye contact ,( in that he could stare out even a retired policeman, who prided himself on it as part of his job with delinquent adolescents! ) were a concern. I'm sure he didn't know why he did it, or why he would guard. That's not how dogs think. It was like aspergers, and I knew it wasn't something emotional that could be cured. Like you say, it's a disability.
I had heated arguments with people who said he was just badly trained.
I suggest avoiding trigger situations. The crate may be one trigger. There is no retreat for the dog when trapped. Your situation may just be part of the adolescent fear stage, but you need to provide a calm controlled set-up. I didn't have young children with my cocker, we had a bombproof Labrador for them, so i didn't have to your difficulty now. I hope things work out, so keep baby gates up to separate them. I had to keep OH from being silly! Could have had a crate for him! Spaniels are very highly strung compared to the terriers I now have, yet one a feral stray, and the other neglected, but both rock solid great with people. My cocker was the best dog I've ever had, despite driving me to tears and near divorce! Be very patient, especially with insisting on a code of behaviour from the humans. They are harder to train. A trainer/ behaviourist will want to observe family life, then give a constructive plan. One who has worked with Cockers would be helpful. Our own Mark, TopBarks, is an expert, based in Yorkshire. You can email him , mentioning Col, and ask for advice on what to do . He adopted a cocker when at the vets, that was in to be pts for biting, and is a wonderful dog now.