I figured this boy's kimono would be good to display for Kodomo no Hi (Tango no Sekku). Unfortunately it is old and the fabric of the front right panel is disintegrating. But the design is still handsome!
The motifs of this kimono are samurai items.
This is a saihai, an item that samurai use to signal troops.
A gunbai uchiwa, war fan, also for signalling troops. The gunbai says Nippon Ichi Momotarou (Japan's best, Momotarou). Momotarou is a folk story, translated to "Peach Boy" in English. Momotarou dolls are often displayed on Tango no Sekku (Kodomo no Hi). Momotarou was especially popular during WWII. I want to say this kimono is probably from the WWII era.
A motif of Kabuto, samurai helmet, also makes me think of Kodomo no Hi (Tango no Sekku)
A fan with Hinomaru design, and an arrow.
I am not entirely sure on this motif. It appears to be a sign post that says 金礼 (kin-rei?). I can't find any translation for this, so my best guess is golden gift? I'm not entirely sure.
Here you can see the damage of the disintegrating fabric. Most of the kimono is fine, but this part is brittle and the fabric snaps apart like ancient parchment.