Church weddings on the whole are part of a larger social event despite their religious appearance. Insha Allah there is no harm to one's faith in attending them relying on Allah, provided one does so out of family obligation together with the intention of inviting to Islam, avoiding drinking and offensive talk and mixing. The Prophet -- Allah bless and greet him! -- is our example, and he entered non-Muslim places of worship for the purpose of inviting others to truth.
Perhaps the real issue is the broader outlook of the couple, since we Muslims view Religion as life: how shall we raise our children, how should we live and die?
It seems to me that the husband must resolve to be the worthier examplar of the couple so as to lead and have a positive effect through his manners and discourse. That is one of the meanings of the man's responsibility of his family. "O ye who believe, ward off from yourselves and your families a Fire..." (66:6). Going or not going here and there is not nearly as important. Allah knows best.