Is it possible to treat a 17 year old wife and a 50 year old wife equally and fairly?

The Prophet (pbuh) told us not to take more than one wife if we cannot treat them equally and fairly. I would like to marry again as I have seen a very beautiful girl, a daughter of my good friend, I fell in love with her at first sight. She is just 17 years old. My friend has offered her to me for marriage and of course I agreed. I definitely want to marry her. The question is , whether to take her as a second wife or divorce my first wife and then marry her? I know in my heart that I cannot treat them both fairly. I know sometimes I will be impartial to my young wife because of her age and her beauty , she can make me feel happy , and I will spend most of my time with her. I will want to buy her gifts and such. So that is just not possible. But also, my first wife and I have been married for almost 30 years and I do not want to disrespect her by divorcing her. What can I do?