How old is the son? Not sure I noticed the age specifically, not that it matters directly.
This isn't a car insurance thing (for you), its a public liability thing.
Personally if it was my car and a dent devils type repair was a thing that would be my preference. The more parts of modern cars that are removed the more chance of a dodgy clip or something and a new rattle or something in future.
When you start taking interior out and door cards etc you in dangerous areas for the future.
If I was the owner of that garage i would be seeing if I could get a dent repair done and then bill for the lot. Could be a really easy win there
Oh edit it was a 4 year old. In that case i think you need to think more about letting them loose in any way around supermarket car parks. People often drive like douches round them for some reason.
I had a 6 inch down into the plastic scratch in my old car. The works fire engine hit it whilst we were outside for a fie alarm. Loads of people saw it happen (as did I), my car physically moved as it was caught. Chips away fixed it, cost iirc £200+vat. Couldnt tell it had happened once fixed which took a day. That was metallic paint as well. He said he could tell it had been done, but no one outside the trade.
In order to try to mitigate it, why not ask if its possible to try chips away/ dent devils etc.
If they can do it, then say you will pay that plus maybe £100 for her trouble.
When I had mine done I had to send photos, they then rang and asked questions, they never came to inspect prior to day of repair. They gave me two choices, repair at mine, or their preferred solution, they would come and pick my car up, take it to their workshop and bring it back repaired, I went for the later, far prefer a day long repair in a workshop than a half day at the roadside.