Thank you all for helpful advice. Rustam - I think you're right that this is very raw for me so now is not the time. But of course I do need to think about it and think about preparing for it.
Cant - I think that your point about social standing is spot on. It is painful but ultimately, on its own, making a friendship for the sake of social standing is not a big deal. The big deal is what went with it and the way my parents probably had a suspicion (as Gary notes) but did nothing. I suppose what I'm looking for is an admission from my father that they were suspicious and a recognition, with hindsight, that they failed in a big way by not acting on it. As I write this, I realise that's probably over-ambitious.
Cant - one thing that you wrote made me think. If I don't tell my Dad and he passes on then the rest of my life will be filled with regret. I can see exactly why you would say that. But I almost wonder if the opposite is true. Right now, my relationship with my Dad is pretty good. That might sound bizarre, but we speak about plenty of things, we can chat about some difficult things, but never about my CSA. So, what I'm getting at is if I raise the CSA issue it might cloud our relationship for the next few years. Perhaps for the remaining period of his life.
My Dad's past 15 years have been hard: he lost his wife to a long battle with cancer, he lost most of his business (having at one point been very successful and wealthy), his best friend and former business partner turned on him etc. So, whilst my Dad's role in my CSA is something he should be ashamed of, I hesitate to introduce this new and difficult issue into an old man's life.
I guess there's a lot more thinking I need to do before I know where I'm going with this. In the meantime, I think I am going to speak to my brother. He is older than me and initially the perp was doing stuff to him and then he turned his attention to me (I guess I was younger and prettier).
I just feel the need to speak to someone who knew at the time. It's fantastic to have the MS community, I have a therapist, I have my wife. But none of you were there.