Your entire post was very informative and thought provoking for me. It also shook loose another possibility in my mind.
It is known that some predatory pedophiles make an effort to look for single mothers to date. They're not really interested in the mother except as a means of getting close to her children.
I started thinking... what if Kyron were abducted by someone dating a single mother from that school?
Even if she hadn't reached the point of introducing him to her children, it would be totally normal for two adults to discuss her kids, their achievements, what sort of school they go to, etc. And, as we have seen, it isn't difficult at all to find extensive information about that particular school online.
I'm assuming that the perp had not been invited to tour the science fair by the mother he was dating but that would provide the perfect excuse if someone spotted him there. "Oh, I had an unexpected opening in my morning, so I decided to surprise my girlfriend by coming to see her kid's exhibit."
That would make the risks of opportunistically scoping out the school seem much lower. He could have gone there without any specific plan in mind but saw Kyron alone at some point and made his move.
I think it is very possible that Kyron could have been lured out of the school building by a "parent looking" sort of person asking him to come help unload something for the talent show. If anyone had seen the perp with Kyron, all that would have happened would have been that the perp would have returned Kyron to the school unharmed.
But there were no witnesses.
The more I think about it, the lower risk this abduction actually was. If I assume that the abduction would have been aborted at any point if there had been witnesses, then it was almost risk free at that time and place.
The perp would not have been expected to be at the school, so it would be easier to arrange an alibi. If someone had noticed him at the school, he would have had a perfect rationalisation.
The highest risk time would have been a few seconds when he had Kyron out by his vehicle.