You will not get into MIT through tennis. You will get into MIT because of your intelligence, passion, initiative, and kindness. Tennis is a bonus but no more than any other extracurricular activity you are committed to. You will not get a boost by being recruited by coaches.
Not straight As is more than okay. Your school also doesn't matter; whether or not you take full advantage of the opportunities there and in your community matters much more.
No one can tell you your chances, but luckily we can easily tell you what you need to get into MIT: The Match Between You And MIT | MIT Admissions
You seem to be pursuing things you are passionate about. That's good. Keep doing that. It will be good to find some way to apply your passions to your community, to take some college courses when you're tired of APs, and to use your abilities in some interesting way--building or inventing something awesome or doing research with a professor at a local university.
Best of luck.