I might just have to stand there and lie through my teeth about raising the child in a 'Christian' household just to appease her sensitivities.
My wife is Christian and recently insisted that our children be baptized. I've always been reluctant on the matter, but our son actually wanted to do it (he's seven) and I didn't feel like arguing with my wife on the matter.
Of course, her pastor insisted I be present, but understood and respected me for my choice to uphold the 4th precept and not lie. I stood up front at the altar, quietly, and just smiled. My son and wife were happy, and the fact of the matter is, I was happy too. Our Daughter being baptized was, quite frankly, not a big deal because she'll choose her own path as she grows up, and so will our son, regardless.
Just my own [recent] experience with it. Maybe it isn't really as big of a deal as you "think" it is? Maybe you can offer alternatives to the Christian ritual, but ultimately, there is no reason to break precepts just to "appease" her -- if your lady cannot understand that, perhaps that also isn't as big of a deal as you "think" it is.
:-/ Good luck with it, and be well, friend.