Here is what I believe may help you a litte better. This I found after seeing all these, good suggestions, but not answers to your question, from Gavin Minnis over on a apple support forum.
This is my recommendation.
Step 1) Create your Keynote presentation.
Step 2) Record your speaking part (separately) with an audio recording program.
I recommend Audacity. It's a great free application. You can download Audacity from www.sorceforge.com among other places. You'll also want to get the Audacity LIB file that is needed to export your audio recording to .mp3.
3) From the Keynote Inspector, under the Document tab, go to the audio section and add your new voice recording file to the Soundtrack.
4) From Keynote, go to File, Record Slideshow.
While the audio plays, click through your slides. This is getting the slide change time down.
5) From Keynote, go to File, Export. Make sure to have the following settings:
Playback Uses: Recorded Timing
Include audio (sound files, movie audio): NOT SELECTED
Include the slideshow soundtrack: NOT SELECTED
Include the slideshow recording: SELECTED!!!
Click next and your Keynote presentation should export to a .mov file (keep in mind, this .mov file has no audio. we'll take care of that in the last steps).
6)Open the new .mov Keynote presentation in Quicktime Pro.
7) Open the original .mp3 sound file in Quicktime Pro.
8) Select All of the .mp3 file and then click CTRL + C to copy it.
9) Go back to the .mov Keynote file and Select All. Then go up to Edit > Add to Movie.
This adds your sound and movie file together.
10) Finally click on File > Save As. Select, Save As A Self-Contained Movie and you're done.
I Hope This Helps!