An internship or voluntary work?

Dear all,

I am new to this forum, so I will quickly introduce myself. I am from the Netherlands 19 years old and studying finance at Bocconi University, Milan currently enrolled in my first year. I applied to the spring weeks of the BB in London, but I got some rejections. I completely understand this is part of the process, but I suspect it has to with my CV/resumé.
Two years ago I moved back to the Netherlands, in order to pursue my dream namely becoming a professional golf player, this included staying with a host family, practicing over 30 hours a week, 15 hours of gym and almost no time for a social life/job. Unfortunately, after some honest self reflection, I came to the conclusion that I should focus on school the next three years and forget about golf.
Because of this adventure, my CV is empty, I just have a high school diploma and some voluntary work projects. I realize that it is vital to get some experience in the real world. However, I spoke to someone in Private Equity (London), who advised to spend my upcoming Summer, doing voluntary work (I can set up a golf related project for children in South Africa), this sounded very contradictory to me.
What do you guys think would look better on my CV, spend my Summer in a bank getting some much needed experience or setting up a golf project in South Africa?