Much harder, but better quality:
1) Demux & convert audio (use software of choice, although BeSweet is popular and free there is a flaw in AC3 conversion that lowers the volume. No fix and this has been a problem for awhile.)
When converting, do NOT use Pal->NTSC, just convert the audio to change encoding.
2) Convert Avi -> DVD at correct NTSC resolution (720x480, etc). Leave the frame rate alone!
You now have PAL frame rate video, PAL rate audio, but NTSC resolution. I recommend AviSynth with CCE, but TMPGEnc is fine.
3) Use DGPulldown to convert from 25->29.97 frames. It takes MPEG2 video elementary streams, and applies pulldown flags to change it to a different legal MPEG2 frame rate. (Actually there is a somewhat confusing way of doing this directly in TMPGEnc.)
4) Author it. You will see little to no slow down in the film/audio. What it really is doing is changing it to 29.97 but it's really 24 fps NTSCFilm internally.
It's what I've been doing, but I'm a stickler.
I will try DivxtoDVD though, it comes from a great company (they make BlindWrite!).