The postcard says these are promotional buttons, but what would they be promoting?

Sara reports that she is off to meet her new students. Summer Sara has left the building.
I’ve been going through the slides at 7611 and scanning ones with people. Most of the slides were from my grandfather’s photographic efforts. He did love a landscape. And he usually captured people from far, far away. Pictures of indoor parties center the people a good 20 feet away giving a clear view of the full table, people’s backs, and off in the background, people’s faces. “Walk closer, grandpa!” I mutter to myself as I’m sorting.
The love of landscape and very far away people is expertly captured in this picture from New Hampshire in the 70s. Who are those people? I will have to zoom in to find out. But look at that tree in full fall color!