OK, you've identified that there are NO OPTIONS and this is what you're doing. SO, you must EMBRACE it. No feeling worried about the 2-year-old, the relationship as being a teacher, etc. This is NOT uncharted territory, it's EXTREMELY common and many large families do exactly what you're doing with even more distractions. I homeschool my first grader with two younger sibs. My extended family has large broods of kids all the way through college who were homeschooled and excelled academically and professionally (they have more free time so start working and doing community things younger and gain more experience)You need to know your goals for the STYLE of education you want him to have. Cyber? Classical? Unschooling? full curriculum? pieced together? Charlotte Mason?...if you're already confident in your choice of curriculum, great, but you should join a homeschooling network-even just online if there isn't one where you live, and start learning from other moms in case you need to make changes down the road. Some moms in my network like Abeka, some don't. Some only use parts of it.
You need to have a well-disciplined two-year-old and a structure. I find lots of moms with wily younger kids give up (because yes, it's IMPOSSIBLE to focus with one kid ripping things up and yelling all the time etc), while the moms succeeding with their various kids have very well-behaved kids. You need a positive attitude and passion for what you're doing. Remember, if you start to feel like you are not offering a great education and teaching him to love to learn, you can put him back in school and supplement his material to stay academically on par. So don't feel trapped!
That's my advice, get the right curriculum for him (you may already have it), join a network, and be willing to change the more you learn about your son's learning style. Personally I love the History of the World history program and Math U See Math program, Writing With Ease, First Language Lessons, and lots of classic literature from library etc. We're following the Well Trained Mind and so far it's perfect for my daughter. But there are sooo many good options.
Embrace it, love it, get ready to spend wonderful time together and learn tons. One of the greatest parts is learning by getting out and doing fun things rather than being stuck in a classroom all the time. Go on field trips-make up your own! Even the silliest local places can provide great lessons.