I would glue or tape them down for the next 24 hours or as long as you can before the show, that should help them stay put for the day. Leave them in until you get to the show site and take them out there if you can.
A while ago, alonsoe recommended using pure glycerin to rub on the ears and help them tip. (You may have to ask for it at your pharmacy.) I did that for a few months after I stopped gluing Ruffles' ears and it was just enough to keep them down. They turned out beautifully. Just rub a bit on the inside and outside tip of the ear. It also wipes off easily if you're going to a show.