A bit of a family unfriendly solution I am afraid. The fundamental question is whether you share values. If you have the same set of values discounting the whole existence of a divine order question then it is a question of semantics. Pay some lip service, go to church on holidays but don't get sucked into the social life of the congregation. Thing is if you are in a sexual relationship, premaritally they are already compromising on a lot of the supposed values. Chances are they will compromise a lot more if you show yourself to be a worthwhile person.
I am a committed atheist, but part of that commitment comes from a profound unwillingness to assume I know jack shit about the underlying order of existence. A commitment to doubt as it were. Part of that doubt involves not throwing my lack of faith in peoples faces. I dated and then lived with a committed evangelical for more than three years. There were just topics I knew better than to broach. I didn't snort or roll my eyes when she started in on that young earth crap or the 'evolution is nonsense' hoopla and she didn't try to drag me to church functions or preach at me.
Almost lost it a couple of times when she brought home creationism defense literature. I was spitting venom as I paged through the book marking factual and logical errors in the margins. But in the end, I realized I was doing it to prove a point that didn't have any relevance on our day to day life. Luckily I was writing in pencil.
Chances are more than even that if you find yourself in a mixed marriage as it were, the catcalls from the peanut galleries of your respective social circles( church folk are about a million times more judgmental and intrusive than their atheist counterparts; also, strangely, far more immoral) are going to me more of an obstacle than each others ideologies. Long story short, if you find that you are engaged in a protracted battle over theology then that adversarial stance is your relationship. Whether you want that is up to you but that sort of relationship is generally not long term or long lived.