RTL only mentioned Henri, MT, MA, MArgaretha, her hubby, Jean and some grandchildren (no names but you can see them next to Jean). They usually mention it whenever Gui and Linus attend things, so I guess it is safe to say that the heir and his wife didn't bother to show up. BTW, this is not the first time that Gui and Linus didn't attend events that were honouring past grand dukes/grand duchesses. I also wonder why Henri's brother Guillaume didn't turn up, it was a weekend, so he clearly didn't have to work. The same goes for the rest of the grandchildren (minus the 4 who turned up), none of them has a valid excuse to miss this. They were also not sitting on the other side of the aisle because the chamber president and his wife (?) were sitting there. From the pics and the newspaper articles that were published so far, one gets the impression that both Guis, Linus, the rest of Henri's children, the Korns and several other grandchildren did not attend.
If I see it correct, present are:
Marie Christine and her younger siblings Alexander and Gabriela. Or the 3rd girl is Maria-Anunciata. At the end of the row it is certainly Marie Astrid.