Your post suggests that you have been away from the church long enough not to know the difference between Christian (the Christian religion) and the act of Christening (i.e. the ceremony of accepting the child into the Christian church). If you are going to have your child Christened then you need to accept that you have to teach the child about Christianity yourself as it grows up.
It would be hypocritical just to have your baby Christened just so, for example, you could get him or her into a Church school.
If however this is your belief and you would want your sone or daughter to get married in church, then go ahead - your child can always change its faith later if it doesn't agree with you.
I agree - you don't have to go to church to believe.
Are you and your fiancé planning a church wedding yourselves?
I have family members who never set foot in a church themselves apart from weddings and funerals, but all their children have been Christened. I think people see it as a sort of insurance.
Whatever you decide - it has to be your and your fiancé's decision, it's nothing to do with anyone else, your critics can do what is right for them, it's your family, nothing to do with them.