The Torodes became liberal Protestants, rejected the premise of their book, and are now divorced. That doesn’t mean they were wrong. I’d recommend you get their book and read it yourself. Open Embrace: A Protestant Couple Rethinks Contraception.
It seems most couples today are cohabiting before marriage. Fr. Dwight Longenecker gives an example, I think, of what NOT to say. Here’s a better resource, Marriage Preparation and Cohabiting Couples, prepared by the US Catholic bishops back in 1999. I’m not familiar with Protestant treatments of this issue.