Unusual Situation - How should I think about business school?

I'm a current Investment Banking Analyst at MS / JPM with an offer for a well-known PE shop that has a track record of placing associates in GSB / HBS. The PE shop is fairly well known amongst the industry with a rising trajectory in terms of prestige.

I am thinking about applying to business school after a couple years in PE and was wondering how I should prepare myself outside of studying for the GMAT?

Although I got fairly great jobs out of college, I am a little worried about my sub-par stats coming out of a non-target (mediocre school) with only a 3.65. A lot of my colleagues have far better stats, so often times, I do feel that I am an outlier. In undergrad, I was so focused on getting investment banking internships / jobs that I was not as active in clubs and organizations around campus (had to work as well on the side). I'm afraid that my leadership experience will be lacking as I apply to the top business schools. How should i be thinking about my application from a holistic perspective?