Not to be the voice of doom, but you could also run into the cranky FAs on a full plane who tell you it isn't their problem. Also isn't UA running UX flights on that route now? I don't know if there is any place to put it on a CRJ.

You could look into getting a long box (I'm sure they have boxes for shipping wedding dresses) and have it shipped. If it is that special, I'm not really sure I'd count on cooperative flight operations (not to mention TSA) at DEN.