Just to clarify, the (possible) full marathon you want to do is 4 weeks from now, and you're also training for a Disney race?
If so...sorry to be blunt, but I think that yes, this would be a really bad idea. I think there was some discussion a couple of pages back where someone wanted to work a half into their training plan. If you look back a few pages there are some good suggestions that you can probably apply to your schedule to do the half.
But I really, really wouldn't do the full. People train 16+ weeks to get ready for a full marathon. Deciding to do it on a whim 4 weeks out seems like a good way to get injured...plus recovery from that full may throw off whatever other training you're doing.