You don't need any special software - just encode the movies in MPEG1 (VideoCD), not MPEG2 (DVD) format. 2 hours = around 700MB at 320x240 (NTSC). A total of around 12 hours can probably fit (6 movies x 700MB = 4200MB). I guess most burning software has an MPEG1 encoder built-in. Since DVD players have a compatibility layer for MPEG1 (VideoCD, etc) this should play back on all standard DVD players.
The quality will blow for sure, which is also made worse by the fact that you're converting from one lossy format to another (RMVB > MPEG). I certainly wouldn't recommend it (since I don't like blocky and non-discernible details), but since you like it this way, go for it.