For a 5:30pm wedding, you want to decorate the MORNING of the wedding, not the night before. The flowers will look horrible. I know this because I talked to our florist about it. We had our wedding at 5:30 and she was there bright and early the morning of our wedding to decorate. It was great. Everything looked wonderful. She did a GREAT job and so, I feel like if she....a professional florist.....chose to do them the morning of, then she's probably right.