Yes, many things said about this case are just hearsay and local gossip. However, in most cases gossip does contain some truth to it (fact with some embelishments). I think everybody is genuinely trying to assist and find out the truth, even those people who post things like "a friend told me", etc.
In my view, it has now been reported by many different people here, that there was trouble in the marriage and he had an affair for 2 years. I tend to believe this. Also, that he was living at his parents home on and off. Sounds feasible, considering the above. The kids could have been with his parents due to him staying there. I don't think the kids were going to a sleepover at a friends house because they are all of different ages. If only one chid was going to a sleepover to a little friends house, then it makes sense, but not the 3 together. I therefore believe the kids were at his parents house (which night? am not sure yet). Possibly Thursday, as reported by hairdresser, which I'm inclined to believe.
I don't think the couple was planning a night out that Thursday. I think they were past the stage of having reconciliatory romantic evenings out.
I am convinced she died at home.