Hi there C,
Thanks for your post. Sounds like you've got some solid work experience (about 3 years so far?), stand-out GMAT, great volunteering experience you can describe with passion and commitment. Yes potentially the GPA is slightly low but the GMAT helps with that, especially at 760, and is more recent. Also MIT is of course a strong undergrad institution.
In terms of what we don't know it would be a) leadership examples; b) results achieved or contributed to ; c) your reasons for the MBA & career goals.
If you put together strong essays explaining who you are, the above points, what you'll bring to the class, why you want the MBA and why that particular school.... supported by strong recommendations and interview, you should have a shot at even these top programs. Of course keep in mind that HBS & Stanford are top of the top and receive SO many qualified applications that sometimes great candidates still don't make it through, especially Stanford which has a smaller class size so is that much more selective. But certainly worth giving it a shot.
In terms of timing, that is a tough call. Certainly R2/Jan deadlines are still reasonable; some places have already been offered in R1 of course, but it's not to the extreme that sometimes is the case in R3 with very few spots left. In terms of putting together QUALITY essays and applications by Jan for that number of top tier schools though, it sounds challenging based on my experience working with candidates for many years. I think you could put together 1-2 great apps by Jan for sure. Maybe 3 with a lot of time on your hands. Also keep in mind your recommenders need to complete x number of online recs and questions/letters etc by the deadlines too. If you have 3 years of work experience, certainly another year is not a bad thing, in particular if you feel you'd make additional progress or accomplish more at work.... a lot to consider and a personal choice for sure!
Let us know what other q's you have and keep us posted. And if you'd like to have an actual conversation, we do offer free 30 minute consults, at
https://www.mbamission.com/consult.php if you are interested. Good luck!