I think as long as you lean a little heavier on the protein part of your wedding dinner, say just have the lean protein and salad rather than including another veg on the side. I think this will compensate carb-wise when it comes to the cake.
Also, you could let your hubby-to-be know ahead of time that you just want cake in your bite, not loaded with icing or fondant. That will help keep the carbs down a bit. I make cakes as a side business and my birthday is coming up so I was trying to figure out how many carbs are in a serving of my favorite chocolate cake. For an 8-9 inch square piece of cake ALONE it worked out to about 28 grams of carbs! So for my birthday, I am making a super amazing cake (want the pics for my website) and having one half serving with some icing/fondant/filling removed and everyone else can have it normal. I'm going to have probably chicken and salad for dinner then have my conservative slice of cake after the super low carb dinner.
another way to go if you'd like to endulge yourself a bit on your wedding day, is slowly increase your carb intake over a week, not majorly but just enough so that your body won't freak out at you (the way it did for the cupcake) for having a few bites of your wedding cake.
My opinion on the low carb cake matter is that you should not be forcing your diet on your whole wedding party. You could definitely try to have one specific tier of your cake be made carb friendly as well, because there may be diabetics or dieters in attendence that would be interested in the alternative and it may be a great advertisement for your bakery to show that they can make a low carb cake.
When is the big day?