I saw many IF photos, and let me said that the only one that almost NEVER smiles was Alix. The girls and Alexei, even the Emperor are the smiling tipe. It's a fake thing that "people didn't smile back then". People seems to think that laughing, jolly etc are modern inventions, and they were not!
Of course, in an official photo, you don't smile, even today...
And well; some Alix photographies show her smiling and even laughing openly! There is a thread in "Alexandra Feodorovna" forum with many of these photos.
Anastasia liked to "play the clown" and to make faces to the camera. Many of her snapshots show them making fun, or making as if she was angry when she was not.
However, in this one, all children seems to be a bit bored or something like this.
RealAnastasia.