The more I find out about the Adelson family dynamics, the more it's hard to understand. So, the mother didn't like Dan--that's established whether she had something to do with his murder or not. Dan was a professional. Well-known. Well-paid. A good father by seemingly all accounts. And the mother still despised him. On the other hand, it seems that the mother was PERFECTLY FINE with her son--a dentist of some type--dating a single mother with children who had a criminal with friends in a gang for an ex-husband.
That's some interesting double standards.
However, digging deeper we can see the difference. To my knowledge, the son didn't have any children with this woman. So, the mother didn't have any grandchildren on that side. But, she had two grandchildren through Wendi. This could be the reason the mother was more accepting of the son's relationship, than Wendi's. In other words, the mother didn't have a lot "to lose" if the son's relationship went bad. With Wendi's, the mother had everything to lose.
There's also this feeling you get with just listening to Wendi's words on that podcast, whether Wendi realizes it or not. To put it in 21st lingo: You get the feeling that the mother thought Dan was getting in the way of Wendi's awesomeness, even while they were still married. And the restriction on the grandchildren seeing the grandmother might've been the final straw.
However, I'm also open to the idea that the son might've taken things into his own hands. He knows his mother is upset. He wants to please her. Maybe he feels like the inferior of the two children. So, what's going to make his mother happy? Killing Dan and getting the grandchildren back down to South Florida.
Obviously, through electronic forensics and other things, a connection will or will not be made to the Adelson family. However, understanding the family's dynamics will be helpful to the police as well. Because I think there's definitely a psychological angle to all this.