Wow, so this guy's probably going to be labeled a pedophile sex offender (and show up as such on those "LOOK AT THE MOLESTERS IN YOUR NEIGHBORHOOD" website databases for everyone to see) for doing something that didn't harm any kids in any way.
What he did is no better or worse than written or non-photographic material that has pedophilic themes, and those can get one jailed and convicted under the theory that it encourages people to think of children sexually, even tho no children at all were involved in their production. Generally, I find that a dubious argument, but in this case children were involved, albeit indirectly. Certainly there could be a higher likelihood that those specific children could be seen as sexual creatures by someone viewing the video than if they hadn't been edited into the video. Not having watched the video, I have no idea if the video actually does that, but the possibility is certainly there, and if so, then the children were harmed. Whether they were harmed sufficiently to warrant criminal prosecution is a separate question I don't have sufficient knowledge of the case to answer, but neither do those of the predictable chorus of libertarians here who are chiming in against the very idea of this possibly being criminal.