French garden-party in the twenties

This is a snapshot I found in a flea-market somewhere in France. It is a small-sized photograph. It's been treated in the sepia tones. I assume, from the clothes, that this photo was taken in the late twenties.

Three couples, having probably interrupted some dancing, are posing for the photograph, together with two ladies playing string instruments, a youngster half hidden by a dancing gentleman, and in the foreground a boy, sitting on the ground, is playing cards.

I just wonder who would make such a family party today, where some members would play without scores and would start dancing on the porch of the house, probably at a small distance of the street, with neighbors who might participate. They look tidy, natural, well-dressed but not fancy. One can hardly guess a shy smile below the mustache of the gentleman in the middle, but on the whole I feel people quietly enjoying themselves in the garden of some suburban house, probably on a Sunday. I would also bet that the lady with the tartan skirt and the one standing by her left are sisters. The violinist may be a third sister.

Besides the boy, all of the participants are staring at the photographer and seem to tell him something. They are firm, decisive, almost intense. The boy's presence, with his playing cards, is weird. He could be the master of the whole game... And what about the mandoline player? Could she be an angel? And the black dressed violinist? And what would these three couples represent? The man and the woman with the white dress are holding tight, they look very resolute. The second couple, in the middle seem to be in full harmony and happy, the third one is a bit distant and projects slight restraint.

You know what? It reminds me of Watteau...