We create DVD / DVD-ROM hybrid discs all the time. The process is simple, just treat the ROM side like you would any CD-ROM. Then on the DVD-Video side, just include a menu item that explains (either using video or text) that if you stick the DVD in your Mac or PC there is more content available. Don't bother with any of the DVD-ROM on the video side features as they are all incompatible with each other and only end up confusing the user.
We created the DVD-ROM features on about 30 New Line Cinema titles as well as several local films including our own title "Done The Impossible: The fans tale of Firefly and Serenity". This title had one of the most complex DVD-ROM features ever built with internet updated content, tight integration with the DVD video and over 8,000 events synchronized to the movie, including an additional 8 hours of supplementary video, viewable synced or separate from the DVD-Video.
Basically what I'm saying is that the sky is the limit when it comes to DVD-ROM, think of it as just a large CD-ROM. You can do something really simple, like just including the data files on the disc, or you can create a more complex "loader" that interrupts the autorun DVD playback with a menu that lets the user view the ROM content or launch the video. If you don't want to figure out how to do that, give us a ring, we have a simple template for doing just such a menu (compatible with both Mac and PCs).
Jeremy Neish
Rivetal, Inc.
801-818-2222