I have a perspective here. My best friend in high school found the love of his life in college. They were great together from the start. She wanted children, and he was vehemently opposed. Eventually, she decided she just couldn't live without children and didn't want him having children if he really didn't want them. (He had once said that if they did have children, they would be her children.) She ended up leaving him to look for someone who wanted children.
The need to have children is implanted very deep in our unconscious. If it wasn't the species would have died out thousands of years ago. At a deep level, we feel that if we don't have children that we cease to exist. And, in the biological sense, that's true. To those who want children, they are our immortality.
In your case, saying we'll deal with this one when we come to it is a statistic waiting to happen. This is one of those things where compromise isn't possible. It's great that your relationship is this wonderful. but in this case, it's like finding a car that looks great, attracts girls, gets 50 miles to a gallon, costs $1,600 and is cheap to insure but has a bomb planted under the front seat. That's not a bargain. Marriage needs to go on hold until you and he are able to resolve this issue. I'm not saying you need to break up, but you need to make sure you're prepared to accept the fact that he may never want children. If he doesn't, but has children to please you, you need to be prepared to accept that you'll be raising the kids while he's on the golf course. My experience is that people who don't want children but have them to please their wife generally end up resenting the children and their wife. I've also seen more than one guy use the kids getting more attention than him as an excuse for an affair. I'm not saying that your man would do that, but it does happen. Ask your older friends.
Ultimately, this is a conversation only you and he could have. Regarding marriage, if you are having doubts, then the answer is "no," or at least "not now."
I know I'm not telling you what you want to hear, but proceeding with this issue unresolved is entering a "fools paradise" as they say. Everything is fine, but the other shoe is bound to drop eventually. Usually, when the woman is nearing the end of her reproductive years.