Can a child opt mother's surname instead of father's?

If you have adopted an infant shortly after birth, you may be able to name the child from the start. If you have an open adoption situation, you may be able to choose a name and have it placed directly on the birth certificate. 

Both parents must go to the Registrar of Births, Deaths, Marriages, and Registered Partnerships to register the choice of surname. This cannot be done by one parent or in writing.

Hope this helps you.