The seating facilities, and of course the fence, suggest that this tea-party, or picnic (though still no evidence of sandwiches), took place in the rear garden of the family home rather than out on location.
Alice is evidently understudying for Deirdre of the Sorrows, her mother of course could never be mistaken for a ray of sunshine, but her father Alfred (as always) looks serene and kindly. Susie (in the straw hat), looks slightly spaced-out, and the boys of various ages (no sign of Bill, Barney or Frank) run the gamut of emotion from A to B, as boys generally do.
But what's going on (as was pointed out to me), between the kettle and the teapot?