In terms of recommended reading, it is difficult to suggest much other than trawling the internet and learning how to read and understand the quality of what you are reading.
www.amazon.co.uk/Choosing-Cesarean-Natural-Birth-Plan/dp/1616145110
Best book on the subject. HOWEVER I do caution the fact by saying it IS very biased in favour of CS and falls foul of its own valid criticisms of studies being biased. If you get the idea of why they are biased from the book you can be critical of the book itself though. Its biggest strength is teaching you principles of reading data rather than simply its point of view. It is easy just to read it on face value so I stress its about understanding why we shouldn't automatically believe the pro-VB rhetoric out there, but rather should try and look at circumstances and how bias (on both sides) is making it very difficult to get a picture of 'whats best' before doing what is best for us as individuals.
I try and be as unbiased on the subject as I can, though I do have a personal point of view so I try and point out information that you need to consider as much to be devils advocate. I don't believe an ELCS is for everyone and I think that often they are being pushed rather than properly understanding a woman's reasons for requesting an ELCS and offering her more appropriate support for her personal situation. I'm not pro-ELCS rather I'm pro-getting it right for woman as individuals. Whats right for me, isn't right for the next person.
So as such as you have already had two vbs be mindful of just how much of a preventative effect a CS will have for you; most damage is done by pregnancy itself and your first birth. In the majority of cases, it will make little difference to women having their third baby by vb.
In terms of safety, generally if you've successfully had a vb, its safer to have another - this tends not to be brought up in most literature on the subject and certainly does not appear in the NICE guidance which is one of its major criticisms.
However in your case because you have had a baby with shoulder dystocia this rather changes the odds and risks to you and your baby. I'm not terribly familiar with the statistics regarding this, but I'd definitely look into it as your focal point in your case as it does change the situation somewhat from what my failing memory serves to tell me.
Its not a straightforward subject by any means, and you can drive yourself half crazy with it.
My gut feeling is that you probably have a good argument that is more accepted and readily valued by HCPs and with luck may not have quite the same battle that others have as a result. (This doesn't mean your case is more valid or 'better' more than its in line with more old fashioned thinking within the profession). I hope that, if you decide an ELCS really is the thing for you, that's the case.