Honestly even though guys can be opinionated at random times about the weirdest things, I really don't think anyone's FI is going to burst out with "I can't believe you got a cowneck, don't you know those are so over? I mean that was so Reem Acra circa 95". Seriously, unless your FI is a designer himself he probably has no clue about silhoutte styles and will think you are the prettiest thing in the world on that day no matter what you wear. With the exception of some, most guys are pretty easy to please. And if he knows you love the dress, then he will love it too. So I say pick it out w/o him and give him a nice surprise. And remember it's not the whole hair done and makeup that gives it the wow factor it's the excitement of it actually being the day you get married.
-Glenda