I'm sure that Disney would be way more than willing to help! This sounds absolutely perfect! I would even recruit some friends/family to video tape take pictures from hidden areas around the spots you choose.
I think I've read before that Disney doesn't like their cast members to interact with proposals just in case the answer isn't yes. That was a long time ago, though, and they've since started doing engagments through Disney Fairy Tale Weddings, so I don't know why they would turn down your business now.
Since you plan to do this at the Grand Floridian and not inside a theme park, you can hire an outside photographer to take your photos. There are some really great ones in the Orlando area. Check out the Arndts, Jess Cumbie and Misty Miotto, for a start.