I met a wonderful guy a year and a half ago, getting married, but there is one huge problem! Advice?

Hi all, I am 26 years old and currently finishing up Graduate school. Over a year ago, I met a man that I fell in love with, and 6 months into our dating, he proposed. However, there is a problem. The problem is, he is about to turn 50 in May. While I don't have a problem with our age differences, it has caused us to have different viewpoints. The main problem is that I want kids...at least 2. He already has kids that are 20 and 21, and has told me more than once that he is not sure that he wants anymore. I have seen him with his kids and know he would make a great dad, but he has told me that he doesn't think he wants to raise anymore children at his age, plus, he has a pacemaker due to some heart problems he found out about a few years ago, and that's made him even more wary of having children because he doesn't think he could keep up with them. I love him so much and don't want to lose him but I also want to experience child birth and child rearing myself. I am not trying to be selfish and I can understand his point of view, but I am also frustrated because he can't see, or is unwilling to see, my side of things. I don't know what to do. Our wedding is 8 months away; we wanted to have it in September on my birthday. So I feel that I still have time to talk to him about this but he just seems so unyielding. What should I do? Should I yield and accept that relationships mean compromise? I want children so badly and he knows this, but he is just so worried about the age thing, which in my opinion, is insignificant. Should we try counseling or something? Would that possibly help? Any advice would be appreciated. I can't really go to my friends or family, because they advised me not to get involved with him in the first place, so if they knew we were having problems, i'd just have to hear I told you so and I can't take having to deal with that right now. Please, any advice?