By all means, do what you find interesting!
When I was an undergrad (13 yrs ago), I spent my time with the obligatory EC's like holding an office in AED, and volunteering with the Special Olympics. However, the hobbies that I pursued after were really what set me apart. For example, I volunteered as a leader with my son's cub scout group for three years, because I was arrogant enough to think I could do it better than the other leaders (wrong, but it was a good experience anyway). I started running ultra-marathons because I was too slow to ever place in a 10K. Rather than volunteer at a hospital, I worked in pathology for 4 years. One of my interviewers asked me about my volunteer medical experience. We chuckeled a bit when I told him that I had over a decade of medical experience, but none of it was as a volunteer.
I'm convinced that the adcoms just want to see that you have taken the time to become a human being, rather than a collection of numbers, unable to relate to a patient.