Scratching another car - Outsurance

Opening your car door and scratching another car is a pretty common thing. My son did this and accidentally scratched the next car. We left our details, the other owner laid a claim with our insurance, Outsurance.

Outsurance says they won't pay because it was a child and children fall under doli incapax, which means they cannot be held criminally liable.

Now I am no lawyer, but I'm struggling to accept this. We are not going to court, there are no charges against my son. In civil matters, we the parents are surely responsible for paying damages caused by our child?

Has anyone had experience with this? I'm finding it hard to trust Outsurance. But then my car has been bashed a thousand times by other people and no one ever admitted it, so this is a first for us.