Please help identify

Upstairs is a rather large old horsehair trunk filled to bursting with letters and photographs belonging to my paternal grandmother. She was born Germaine Levêque in St Vaast-la-Hogue in 1892 and was educated there and in Cherbourg, France. She worked as a teacher and governess in England, Germany and Switzerland before leaving in 1916 to marry Hans Lehner. Around 1920 he bought the house in Hingham where my parents still live. She had 2 sons, and then around 1930 she and Hans separated. They never divorced, presumably because they were Catholic. He stayed in Hingham and raised the boys, while she went from city to city, from hotel to apartment to hotel. Thus far, and I am far from finished, I have documented – via the envelopes of her correspondence – twenty different addresses from 1930 to the 1953, when she more or less settled into the Hotel Vendôme in Boston.
It is not entirely clear why I am in possession of this trunk, which presumably went from place to place with before coming to rest at my parents’ house around the time she died, in 1978. But I can guess: no one but an archivist manqué would take it on.
This is a selection of items I found this morning:
• In her tiny French script, a list of US presidents from GW to FDR
• A sheet torn from a 5-year diary, for March 15. The first four sections are empty. The last one is marked 1948 and reads: Monday. Feeling much better. Strange dream about Duke of Windsor and deep chasms!!!?
• A picture of my father and his brother (circa 1930) on their pony cart in front of the Orchard. I happen to know the pony’s name was Major, as that was one of the memories that as most vivid for Dad right after he had his stroke.
• A photo of Germaine standing in front of an airplane: Imperial Air ways, London. G-EBO. There is a uniformed, capped man standing next to the gangway; otherwise she is alone on the tarmac. She is carrying her hat which looks unfortunately like an upside down chamber pot. I think she was going to or from Greece because it was in a pile of photographs of Greece, in some of which she is actually wearing the aforementioned hat. From Wikipedia I have learned that the plane was a De Havilland 66 Hercules, a seven-passenger plane built in the 1920’s and retired from service in 1942. With a maximum speed of 127 mph and a range of 525 miles, it was obviously not used for transatlantic journeys. There, with a keystroke, are more facts about the plane in the picture than I seem to have about my grandmother.
• And this mystery group picture. Like almost every other photograph among the 100’s in the trunk, this one has no identifying names or dates. Who are these people? What is this gathering of apparently various folks? What brought them all to this nameless place?