I always love vintage photos of kids. They generally make much more natural (i.e., less guarded) subjects than do adults.
Halloween party, possibly Children's Hospital
Kiddies in wading pool
Kids eating
Kids in Boston Common Frog Pond, 1940s
Kids sledding on underwater ice in Charlestown, 1921
Little boy and collie
Little girl with umbrella
[these captions sure are prosaic, aren't they?]
New sprinkling device used by the city of Boston for the kids on hot days, 1921
Pie eating contest
Two children with dog
Courtesy of the Boston Public Library, Leslie Jones Collection