And Hodges Gallop, to be sure! These kids are about the same age as my grandfather, who was born in 1897 and had his one daughter fairly late in life, 1944.

The bikes... They all have bells. One has a (kerosene?) head lamp. But other than that, they are quite stripped down. No fenders or chain cases. I can't see a coaster brake arm... does that make them fixies? They have swept handlebars that are about level with the saddle. Some of them are clearly too tall for their rider, others look about right, but none look too small. The tires are medium sized. Probably a lot of cobbles and dirt in 1911.

The geometry is quite raked out, look how the top of the tire is higher than the fork crown. Some Powerpoint engineering places the angles at about 68 deg but the seats are cantilevered in front of the post instead of set back like a modern bike. They're quite long, too, with a fist of clearance between seat tube and tire.