unfortunately I dont think there is a way in the current Prezi editor using paths / frames. The only other way I can think of doing this would be to manually start the video when you get there - have no path point on the video and click the player start button. When you have done this move to the next frame (placed directly on top) to fade in your text on top of it - - a bit sloppy but it should work.
You could of course have text come in alongside the animation as part of the video, but you would have to time it right on the day.
Sorry I cannot help further, maybe another user can come up with an idea for you?