I hate to be dismissive. But so what? The interesting thing is if the child has come to harm or feels exploited now or in the future. If not, then who cares? I'd argue that the intent is important.
If you have to stop doing an act because it could potentially be used as porn to someone, you'd be completely paralysed from creating anything. Any person would be banned from appearing on camera or picture ever. Seriously. We all know fetishes vary a lot and can be really weird. ...paedophilia I'd certainly put among the really weird ones. I'd say fuck it. If they want to wank over holiday family snap shots they find on the net, good for them. I think it's distasteful, but trying to stop it legally will just do more harm than good.
In Sweden today we have a legal situation where a person who is below 18 and takes naked pictures of themselves, (which is all of them in today's age of digital cameras) and saves the pictures on their hard-drives, has to erase them when they turn 18 or they put themselves in a position where they can be put in jail for having child pornography. This is paedophilia witch hunt completely out of control.
I've got no love for paedophiles, but I think we should focus on the children. If they've come to harm, then we should get worried. If not, then we should back off no matter who's wanking to what. I think a good motto is, "only fights battles you can win".