So basically this is your one free summer break. If you WANT to do research, do it. If you have your heart set on traveling, do that. I won't lie — it's pretty tough to juggle research later on during second or third year but in your fourth year you get 3 (yes THREE) months of free time to do whatever you want (usually reserve some of that for interviews though) and you can actually take research electives and get some experience in that way. Maybe you can even get both medicine and travel simultaneously…travel to a third world country and work at some clinic. If you're worried about your resume/cv then at least you would be able to say that you've personally witnessed health care in a third world country/somewhere else other than the U.S. Around January the OME has a noontime session where they briefly run through summer research programs students have done in the past. Later on in the year some student clubs do another noontime session on volunteering in other countries (I think it's the Family Medicine group/Hands Across Borders). And finally if you just want to use your first summer to go visit family somewhere, DO THAT. Hey you have the rest of your life to be a doctor, but when will you have an entire 10 weeks to travel without obligation? Sure medicine is getting more competitive, but remember that you're choosing your life, not the other way around. If anything, remember that.
research vs travel