Export 24fps timeline to 25fps

probably be ok, but what I do is "interpret the footage to 25fps" in the clip: modify menu and edit into a 25fps sequence before you bring the file into your sequence.  You may be able to do this on the timeline (I don't know if this is the case)  This will make sure your video is playing out smoothly at 25fps (you're just changing the playback rate of the file).  I think the audio on your timeline will have a slightly different sampling rate to adjust for the change in frame rate, but the export should handle this issue.  I've used this workflow with feature films to adjust 24 fps to 23.976 for use in authoring dvds without any issues.  I've just finished my first cup of coffee this morning, so hopefully I've explained this clearly.  If not, post back with any questions.