That is a great idea!!! I think that is something your guests would actually be able to use, which is important. I hate favors that you look at and just think, "Well, this is nice. But it's just going to be one more thing to add to my clutter."
As for getting them in bulk...the only way to get them on discount would be to be a Disney Cast Member. Though you may want to contact the resort your guests will be staying at and inquire there.
~Lindsey