First off, congrats!
The first thing you will realize about marriage is that you will have to do more compromising on one issue than you have ever had to do in your life. It is a must and the only way a relationship will be able to last all sorts of storms.
The thing is, I understand where you're coming from. I was a little girl once and literally planned my entire wedding before I ever met my husband so I know that need to fulfill a dream you've had for so long. As women, we tend to hi-jack all things related to weddings, but forget that it's 'his' wedding day too. Even when they act like they don't care, they do, and would like to be considered in the plan and have some say in what happens on the big day. It's only fair and if you ask me, a great indicator of how he'll approach marriage in general, so embrace the fact that he has an opinion.
I am not privy to the inner workings of your relationship so it's a little difficult to give clear advice on how to approach the matter. To me the cleanest solution would be to take the wedding to neutral ground, a non religious place such as an outdoor wedding or at a non-religious venue. If you have your heart set on this venue however, and really want to fight for it, you must make him an offer he can't refuse. What are you willing to compromise, give of do in order to get him to give you this particular win? Get creative.
There is another way to solve this issue that may involve a little manipulation which is excellent practice for use in your marriage. ;-)
When he's in the mood, bring up the fact that you'd like him to have a say in the wedding and would like to make sure that you both get what you want out it. Have him create a list of 5 things he wants in the order of importance. On your list, make sure you place Venue at Pent. Church at the top. More than likely, that will not be at the top of his list. Once you compare notes and venue isn't number one for him, you can proceed to negotiate from there. You would win on the venue because it is ultimately the most important thing for you, and he can have whatever's at the top of his list, even if its wearing sneakers with his tux. You've gotta give something!
If by some crazy miracle both of you are gunning for that venue, then you might have to whip out the good underwear. Lol!
So my advice is, be willing to compromise yourself, be willing to give up generously to get what you want, make him an offer he can't refuse or manipulate your way through it. Pick your poison.
Hope this helped!