It's not too hard to do, you have the rip the DVD using a program (MacTheRipper is free and works well), then convert the resulting file(s) to the optimal resolution/frame rate for the iPod. There are a lot of new programs popping up that will do that for you too. The question is whether the resulting movie is great to watch or not. It's not as good as say watching a movie on a PSP that's on one of their new discs, but it's supposed to be not too bad. Another question would be what will happen with the next generation of iPods...people generally assume that they'll be MUCH better for doing what your son wants to do.

The new iPod can only playback movies encoded with very specific settings. After ripping the DVD with MacTheRipper, you can encode H.264 video (which gives the best quality) using HandBrake - but only using the latest unofficial release of the software that encodes using the Baseline Profile (see the HandBrake forum). Or you can use something like Cinematize to convert your .VOB files to a QuickTime format (like .DV), then use QuickTime Pro to encode H.264 video (which has a "Convert to iPod format" menu option).

P.S. Circumventing personally owned DVD encryption is theoretically illegal according to DMCA legislation.

Edit: forgot to mention that encoding a full length movie to H.264 video using a G4 chip will take from 12 to 24 hours to process.

From the Apple site:
H.264 video: up to 768 Kbps, 320 x 240, 30 frames per sec., Baseline Profile up to Level 1.3 with AAC-LC up to 160 Kbps, 48 Khz, stereo audio in .m4v, .mp4 and .mov file formats
MPEG-4 video: up to 2.5 mbps, 480 x 480, 30 frames per sec., Simple Profile with AAC-LC up to 160 Kbps, 48 Khz, stereo audio in .m4v, .mp4 and .mov file formats