Bathing is normally forbidden on Tisha Bav. May one bathe children on Tisha Bav that is a nidche after chatzos?
Regarding the nidcheh:
When Tisha B'Av is a nidcheh, all restrictions are permitted immediately with the conclusion of the fast on Sunday night [including bathing, shaving, music, etc...], with the exception of consuming wine[other than for Havdala] and meat, which become permitted at daybreak of Monday morning.
1. All bathing for pleasure is prohibited even in cold water including the hands, face and feet.
2. Ritual washing upon waking, after using the bathroom, touching covered parts of the body or before praying is permitted, but only up to the knuckles.
3. One may wash dirty or sullied portions of the body (including cleaning the eyes of glutinous material), and if necessary may use soap or warm water to remove the dirt or odor.
4. Washing for cooking or for medical reasons is permitted.
5. A woman may not immerse on Tisha B'Av since relations are prohibited. Washing to commence the clean days is permitted.
Rabbi Shimon Eider in A Summary Of Halachos Of The Three Weeks on page 32 says that bathing is not permitted until Sunday evening when the tenth of Av falls on a Sunday. He does not differentiate between adults and children.