Not sure this will be useful, but I'll throw in my .02.
I've had some tailbone and public bone pain that are basically gone now . . . things got a lot better once I started noting when it hurt and narrowing down some causes (hard surfaces or bad posture). Katy's blog on this website helped me a lot.
Specifically, there was a post about not sitting on your sacrum, which I was completely guilty of doing and once I stopped, my tailbone pain went away. I looked for the exact post but couldn't find it and only have a few minutes. Long story short, every time you sit you want your pelvis positioned so that you're sitting tall and your bum is sticking out a little. Sitting on an exercise ball puts me in the right position automatically. Sitting on a deep couch or in the car, or slouching, pushes my pelvis to curve the other way so that my sacrum is kind of curled under and some of my weight is on top of it - then I'm in pain when I get up.
As for tailbone dislocation, I've also thought about that a bit, it may well be the part about the birth that I am least comfortable with! My plan is to keep off my back and try to give my pelvis the best possible chance to open so that there's less pressure on the tailbone.
I'm eager to see the other responses you get. Hope you find something that works to relieve the pain.
I was having awful tailbone pain and have been seeing a chiropracter for a month. She diagnosed that for me, the tailbone pain was directly related to my hips being inflexible (a long time established condition for me; I work on hip openers a LOT in my yoga practice because it is such a restriction in my body.) She worked on doing some cracking stuff in my lower back and instructed me to rub hard down my outer thighs and practice more hip opener excercizes, so I have been practicing pigeon more often and other hip openers. I've read on excersize blogs that that is a stretch that helps a lot of people with tailbone pain, so if you can do it, maybe it might help. I no longer have tail bone pain. If it is an option for you, you may consider visiting a chiropracter as she may be able to diagnose why you are having the pain and help you to get rid of it. The internet is a terrifying place if you look things up in english on google.com with the word "pregnancy". When I look my same questions up in Norwegian on google.no, the internet is WAY less terrifying and has more practical information. Just trying to say that there's no reason to think your tailbone pain will automatically increase your likelihood of a C-Section. The english-language internet is dark and full of terror :).
sorry for what looked like a short response! I was on the ipad with a cranky 10 month old and a sore tailbone/butt! The chiro has done wonders helping my hips feel better and my back, but the tailbone has had only minor improvement... which I guess is better than none. Im less worried about how I feel going through the pregnnacy than I am worried about it possibly affecting my home vbac plans... I guess I was mostly looking for anyone who has been able to have a successful unmedicated birth with tailbone problems.
If you couldnt tell.. Im a little more than paranoid about anything that can affect my home birth plans! I just cant bear the thought of another c-section. If something comes up, of course I will submit (unhappily) to another section knowing that at least I was able to try, but hoping for the best!