I say no way to this one.
I have been doing all my dress shopping alone so far and it's actually easier than you would think. I go in, try on 20 dresses, and am out in an hour. I immediatly know if a dress is a yes or a no - no advice needed. I think it would be so much harder if I had 5 people (or even just FI) with me saying everything looked beautiful. Guess what, every dress doesn't look beautiful.
I think you should try to get one person to go with you if you really need it, but not FI. You only get that surprise factor once in your life. You don't want to tell your kids "the first time daddy saw me in my dress was in the David's Bridal dressing room."