I've spent a lot of time reading the full thread as this is something that I didn't really know about before (not naturism obv, I mean naturism involving children).
So sorry to hear of PP's distressing experiences 
I understand the points made about body positivity/freedom etc. But I must say the idea makes me uncomfortable for several reasons. I appreciate the point that children are more likely to experience abuse from, say, a football coach. My concern would be that a child who believes it is normal to be naked in front of adults they don't really know and for those adults to be naked in front of them may be more vulnerable.
I do find it surprising that some posters don't think it's more likely than other events/locations to draw paedophiles. Surely, any event where children are going to be naked is going to be attractive to people like that.
I'm also concerned about consent. We can never really know what our children are thinking privately, no matter how sure we are that they're happy and comfortable. Children generally want to please their parents, and if the parent clearly sees naturism as an important part of their life, the child may start to feel that they don't want to attend but keep going so as not to upset their mum or dad. This wouldn't even be an indication that the parents were 'pushing' the child to go- if a child gets subtle messages that this is a good thing, the way our family lives, it's important to us, it may be harder than some parents may realise for them to speak up and say no.