Assuming for a second that the father/husband is completely innocent, this is a common FBI technique, to have a memorial service held. While the service is going on, LE photos the crowd and writes down license plate numbers, often even checking the license plates of cars passing by. The perp will sometimes go to these services. IF the local LE thought of it, they may have even photographed the funerals and written down the license plates of those who attended. Sometimes LE will organize a tip line thing manned by local residents in hopes that one of the volunteers manning the phone will be the perp, and of course they'll run checks on those who volunteer to man the phones. Ted Bundy did that, he manned the phones during a tip line thing. Perps often like to find a way to insert themselves into the cases.
Even though LE says the dad/husband isn't a suspect, that doesn't mean anything. LE will often say that in order for the perp (in this case possibly the husband/father) to lower their guard and hopefully slip up.
The above ideas comes from several of John Douglas's books. He pioneered profiling while in the FBI.
Does seem strange to me that the son received the worst injuries. Has LE said whether either the step-mom or son were molested or posed? And if it wasn't the father/husband who committed the murders, the boy could have opened the door to a stranger without even thinking of possible dangers, which would allowed the perp access. I've always preached "safety" to my kids and we've always lived in a small, fairly safe town, but you never know. Too many sickos in the world today to even pretend we're safe.
