shadowing is useless. 3rd and 4th year is exposure to medicine, and much more than shadowing. don't waste your time.
if you wanna do peds, IM, family, etc. just enjoy your summer. if you want to do something competitive do research. many research opportunities are available with very decent hours so you can still enjoy your summer break.
i wrote two chapters and helped publish an article (2nd author) while still having plenty of time to drink 3-4 days a week, hit the gym daily, visit high school/college friends, and see family.
edit: enjoying your summer may also mean volunteering in the amazon. if i wasnt hell-bent on surgery, ida totally have done that.