Hello and thanks for your post.
The application process is truly holistic, and committees will look at your stats (GPA and GRE), work experience, and extracurriculars.
You are right that your GPA is below average, but your GMAT is very strong and above the average at even those top schools, so that does compensate for it a bit. Also, if you had more time (and happen to apply in the fall), you could take a supplemental course such as stats or calculus, or HBS CORe.
It is hard to gauge your work experience without knowing your accomplishments and impact you have made there. Based on your age, it looks like you probably have about 5 years of work experience, so that is good. It is important to have at least 5 (upon matriculation) for schools, especially GSB. It will also be important to explain why you want your MBA, and to also illustrate the skills you already have which are transferable. Be sure your story makes sense, and is realistic and specific. Your long term goal of course connects with your short term goal, and hopefully that short term goal somewhat relates to what you have been doing.
Regarding extracurriculars, make sure to really emphasize your leadership roles you have taken on. Your significant mentorship of 5 years is impressive.
These schools are extremely competitive, but I do think you have at least a chance. I hope you apply. I also want to mention that you would be in good shape for Round 1 in the fall. You could take a supplemental course, and increase your impact at work. Either way, I suggest applying to several schools, including reach, target and safety. Hopefully they will see that you have a compelling story and are someone who will add value to the classroom and community.
Good luck!