Do you use conditioner for your girls' hair? If so, at what age?

Usually shampoos for babies and kids are sufficient and there is no actual need for conditioner. Personally, I think that's enough until they are about 10, unless they have curly hair that requires special attention. But if you want, you can get those that are meant for babies and kids. The brand California Baby has a good range of shampoos and conditioners that are gentle on baby's hair and scalp.