I feel sorry for guys. It is so much pressure for us because of the women and there are too many things that are cliche now. Restaurants are horrible, in front of the Castle has been done a billion times over. If it were me and I was going to propose at WDW, I would find something completely new to do...
Play a round of miniature golf, hit your ball in before she does, take your ball out and leave the ring in the hole for her to find when she hits it in.
My all time favorite would be right before the drop on ToT or right before the launch on RnRC.
Maybe a little cliche still, but a fireworks cruise and propose before wishes.
Best yet would be to work with WDW to see if you can dress up in her favorite character costume and in a very secluded place, propose as her favorite character. This would take a lot of coordination and luck.