Which one is your child? That one. The one raising a hand.
Which child is yours? That boy/girl over there raising a hand.
Which one is your child?
どれがあなたの子？
That one. The one raising a hand.
あの子。手を挙げている子。
Which child is yours?
どの子があなたの？
That boy/girl over there raising a hand.
あっちで手を挙げている男の子／女の子。
たくさんいる中でどれ？という時は Which を使います。
答える時は child というよりも boyかgirlで答えるとより親切だと思います。
日本 
