I quite often put 2 converted AVI's on a DVDR. Putting 3 to a DVDR does not produce good quality conversions. However, if the movies are only 1 hr long each, then thats possible. 4hr of movie is the absolute max I would fit to a dvdr.
In the bitrate tab of DVD2SVCD I've suggested 4400 for CD size, just 1/2 it for 2 or 1/3 it for 3. Then Author in Maestro or DVD Lab by loading each encoded set into its own Movie within and then incorporate a Menu for selection.