Wow, I can't even imagine doing my wedding in the morning and then coordinating everyone to get through a reception breakfast, get changed, and get to Port Canavrel. The boat may not leave until late in the afternoon, but if you are doing Disney transfers they have pickups that can start as early at 10:30. They dictate your pickup time, not you. If you DON'T do Disney transfers make absolutly certain you get to the port on time. The boat will only wait for the Disney motor coaches (supposedly) if there is a problem with one of them reaching the port on time.
We were at Disney at that time this year and it was very very cold (it rained on that day this year). I was miserable doing our BP shoot in late January; I can't imagine how miserable I would have been during a wedding. Our wedding day was beautiful though so its just luck of the draw. (ETA: miserable uncomfortable and cold, not emotionally miserable; I was elated, LOL)
WDW can make a lot more things happen (for a price) than
DCL can. The ship is confined within itself and there may be some requests they simply can't accomodate as they can't just "get more" so to speak when floating at sea. There are all sorts of Coast Guard and USDA rules and regulations.
At any rate, I don't mean to sound negative either, just giving you some things to think about. Your plans sound lovely, and I think it's wonderful you are doing so much for your guests. Try not to stress too much and remember that it is not selfish to think that your wedding day really is ultimately about you and your DH. Make sure it is what YOU want, not what you think will please your guests the most. You don't want to regret it later.
Excited to read more!