Congratulations! You're almost there! A lot of breech babies turn on their own, and versions by a skilled and knowledgeable practioner often help.
There are a lot of pluses to a vaginal birth. A c-section is major abdominal surgery and carries all the risks of that. It affects your options with future births. You'll have a faster recovery time with a vaginal birth--which would help with two!
Weight estimates before birth are estimates--they are always guessing wrong! Ultrasounds have a 20% margin of error. A ten-pound estimate could be 12...or it could be 8! It does sound like you grow big babies, though.
Even thought it's been in thenews, dystocia is a fairly rare complication, even in larger babies (5 percent I think). And there are ways of handling shoulder dystocia.
My second baby was 9lbs 8 oz and the doctor on call used the "McRoberts manuever" just in case of dystocia (there was no indication). I was squatting and he basically had me slammed on my back with my knees up as far as they would go for the last push. I still don't get it, because it was the exact same position as the squat, just on my back. The general idea though, is to be in a position that moves your pelvic bones apart. (They move anyway, just some positions help them move effectively.)
The Gaskin manuever is also fairly successful. Ina May Gaskin delivered something like 3,000 babies with a 2% c-section rate, so it must work!
I think it is great that your doctor is advising you and letting you make decisions about your medical care. I think it's great that you're educating yourself! You might consider talking to a doula or childbirth educator (Bradley or Brio) in your area. Most of them would talk this over with you as a courtesy, and explain in more detail what it all means and what your options are. In the end, you need to be comfortable with the option that you choose!
And I know plenty of people who delivered big babies with no problems at all--my mom had two that were 10 lbs+, my sister-in-law had a ten pounder and there was my "little" guy, all just in my family!