The right answer to an interview question is sometimes obvious. If they did not expect you to work in the night, they would not inquire about this option in an interview with you.
Twelve-hour long shift and working in the night belongs to the work of a hotel receptionist (not so common in an office receptionist job though).
You should show some flexibility in your answer, telling them that you are ready to work in the night. You can elaborate on it with your experience with night shifts, or with other things that relate to your availability.
I can definitely work in the night. I do not have children, and I am used to go to bed late. What is more, I can maintain a good level of concentration in the night, and I will not struggle to take care of my duties.
I would not mind working twelve hours a day. In my previous job it was not uncommon that I worked even fourteen hours a day, when someone got sick and they asked me to stay longer in work. I have read your job description carefully and know that receptionists do twelve hours long shifts in this hotel.