Do you and your DC never go to friend's houses Cinnabar? Would you really sue a friend if you got injured at their house?
I wouldn't want to. I'd avoid it if I possibly could. But suppose I got the kind of injury that stopped me being able to work. Or, worse, my DC was left paralysed and needing 24 hour care. Then, yes, I would sue. I would have to, to get my DC the money they need to secure their financial future.
And I wouldn't feel bad about it, because I wouldn't actually be suing my friend. It would be a claim on his/her household insurance.
But that's assuming that I was on my friend's property for social reasons. The OP may well find that her friend's household insurance wouldn't be valid for a similar claim because the insurance company (who don't give a stuff about HMRC, frankly) would see it as a business arrangement.
We certainly had to extend the terms of our household insurance when we took on our nanny, to reflect the fact that if she were injuried in the course of looking after our children then it would have been a work-related injury.
She also had to amend the terms of her car insurance because she takes our children in her car. We make up the difference in her insurnance costs when she renews each year (i.e. her insurance company provides her with two quotes, one for normal social use and a second to include business use).
All this might seem hard nosed - it is hard nosed - but you have to think of these kind of things in business.