I think Smith went way too far, but a dark and unoccupied house is not what I would call a “tempting target,” an attractive nuisance. It could only tempt those already criminally inclined.
My point is that he planned this all out as best he could.
He clearly would have been very disappointed if, after all that work and effort, he didn't get to kill at least one human being.
Those kids literally made his day.
He probably felt like a kid at Christmas when his CCTV motion cameras lit up.