Actually, what you need to do is make 100% sure you have the video and audio done in a format that accomodates the capacity a dual-sided DVD. That ensures you have the highest quality possible, and sets you up for the future.

And from that base, there are many programs (like CloneDVD) that takes EXISTING dual-sided data and then filter it down for single-sided DVD duplication. If you want to produce a single-sided DVD, then filter down from the original, and distribute that, and this still leaves the option of a serious dual-sided version from the raw data.

Another key element is that these filter-down versions are of excellent quality when using dual-sided digital data, most times superior to down-sampled, imported video.