From Rose Reiton's diaries, we know the missionary families held birthday parties for their children, with children from other families invited. In this year (1937), Rousseau's four children would have been these ages:
Morrison 23
Elizabeth 20 - May 10th 1917
Evelyn 14 -
Sybil 12
They are probably in this picture. The tall young man may be Morrison. We know Elizabeth Rousseau and Helen Reiton (from Kowloon) were of an age, good friends and often in each other's houses. Evelyn Rousseau and Esther Reiton were also friends of the same age but younger. The Reitons could be here.
On Friday February 19th, 1932 - Helen and Esther Reiton went to Evelyn and Sybil Rousseau's birthday party.
Other family names possibly in the picture are Kehr, Crane, Hensley and Morrison, but they may well be Kowloon/Victoria families that the Reitons knew.
Note hardwood doors and window frames.
Thread here.
Thanks to Nick Marsh for the picture.