I agree with Karen's suggestions. One suggestion, I'd have your Mom help you with the wording but I think you should write the note and send it to them. It makes it more personal when you state "your day would be incomplete without him and his wife" in your own handwriting.
The only other thing I'll say is - this is your and Brian's day. What you want should be most important. Family should be involved but if you prefer this ceremony, they should understand and be respectful of your choices.
The dress is gorgeous!! What will Brian wear?
Bookmarks