There's no mechanism for me to be on the road while she's on the pavement. I have to choose so I choose what I think is safest in those circumstances. In others I choose what is not safest. I ride those roads on my own partly because I'm faster without the trailer's weight and less of an obstruction without its width but also because even though I would still be safer on the pavement, my reflex is much like yours - I should obey the law. And most of the time I do. But I can understand the reluctance to say that it's OK to be on the pavement in those circumstances because once you identify one case where it's OK, the door is open to other specific circumstances. And then we're on wingpig's slippery slope.
I guess I'm starting to wonder if that's such a bad place to be. I suppose I have to say that or accept my own hypocrisy in thinking that its OK for me to ride on the pavement (in my limited child-transporting circumstance) but not for other people. More generally, I'm wondering if we're willing to protest about the need for roads to be safer, maybe we should also be less condemnatory of people who use other, albeit illegal, infrastructure. Otherwise, we're saying that people should either ride on roads they believe (and we agree) are unsafe or stay off their bikes until it's all been fixed.
I think the accepting coppers are interesting because, on the whole, humans make better judgements than machines. I'm sure they look at me and know that I'm breaking section whatever of whatever Act. But seeing me pulling a child (and the child is what saves me) they smile and let it slide. The legality may be a dichotomy but the system is grey. Even if I meet the copper who would want to charge me, there's no PF in the country that would proceed with it.