Sensible format to create audio DVDs in?

I've recently bought some MP3-CDs (audio book) and as I don't have a standalone player I want to convert them to DVDs. I'm comfortable with transcoding audio and creating normal video DVDs, but this is the first time I have tried to create a DVD just for audio content. From searches, I have the impression that DVD-audio requires a separate player, so it is probably best to create a DVD-video with e.g. constant black background. The audio book comes to 1.8 GB, in 44.1 kHz ~128kbps stereo* MP3s; I was thinking of resampling to 48 kHz and then reencoding to either MP2 or AC3 at ~256kbps. Does this all seem sensible? Am I likely to hit any problems playing back on some players because of the video bit rate being too low? Any advice would be much appreciated! *(not sure why)

Sounds quite sensible indeed. No, there shouldn't be any playback issues on standalone players. The type of presentation you're creating is commonly referred to as a slideshow, which is one or more still images with background sound. Many simple DVD authoring programs are able to create slideshows. BeSweet is good software you can download here for resampling and encoding to AC3/MP2 in one step. Any bitrate starting from 192kbps is fine for stereo sound.

Many modern DVD-Video standalone players play MP3s, for example the philips dvp-642 which you can get for ~ $45.

I don't think you need to use 256 kbit if space is an issue, 192 should be just fine. DVD commentary tracks are commonly encoded at this rate. For authoring I'd use MuxMan, you can specify a 720x576 bmp and set the duration to something long. Plus you can make a template project file you can reuse, if you want to repeat this operation in a scripted manner.