(I'm posting with my wife knowing, under her name)
Anyways, coming from a dad who was scared about being in the delivery room also; I AM SO GLAD I DID! to be the first one to see that little bundle of joy is amazing. Here is a little about myself, I am from a small little town (pop. 2100) I grew up on a farm raised by a set of very old fashion parents, I did time in the military and now is a police officer; needless to say I was one who was far from the of natual child birth thing, I was raised thinking the mom gave birth in a hospital and the father stayed in the waiting room with a cigar and was told by the doctor what the sex was. When my wife told me she wanted me in with her during birth I said oh NO never going to happen! She asked me why, I told her honestly, it was gross and I only want to see her in a attractive way (if you know what I mean) well after many talks (MANY!) she convinced me to be there. Well by my personal experience when my little guy was born, never once did I think anything was gross or weird, actually it was amazing. I was next to my wife the whole time and even helped out the midwife during the long hours of contractions (I was the leg holder). My first advice to you with talking to him is- tell him to suck it up and deal with it! like I learned birthing is mainly for the Mom and the dad is there for support, and the dads presence is VERY important, and that he should be thinking of someone other then himself at that time.
My main advice for you, tell him there are a lot of MILFS in the world and birthing will not mess up his mind (sexually) I promiss.
Good luck, hopefully he will be there, it will suck for him to miss it.
also...I have gone from being sceptical about even being in the same room at the hospital, to now being an excited part of planning our next..as a home birth!! Man how things change!!