Shichi-go-san is a Japanese festival for praying for the healthy growth of young children. Girls attend the festival at the ages 3 and 7, boys at the ages of 5 and 7. The festival is held on the 15th of November every year. However, most people celebrate it on the nearest weekend since it is not a national holiday.
On the festival day, the kids come to a shinto shrine accompanied by family members, dressed in kimono. However, a few children dress in western style.
The priests take the children and the family members in to the shrine and conduct prayers, usually 2-3 families at a time. A praying session takes about 30 minutes.
Chitose-ame (candy for longevity) are given to the kids by both the parents and the shrine. At this particular shrine, they got ballons too.
Every kid climbs on to the "big stage", after the prayers.
They take loads of photos with family members. Later, each of the kids goes for a studio photo with the costume and candy.
A few random photos. More photos at my niece's blog
These photos were taken at Hie shrine in Akasaka, Tokyo. Any large shrine will have quite a few children coming in, if you are in Japan during the week that includes the 15th of November.