Toast will convert the file for you, and it will take a long time. You need to have at least version 8 (9 is highly recommended, 10 is optional).
You can save a bit of time by using a free program called Redux Encoder, which should be able to handle most file types (including MP4). It too will take a while, but you set it to convert from MP4 to DVD (video_ts), then drag the Video_TS into toast and a few minutes later (depending on your burner) you'll have a "real" movie dvd.
One final note: several newer models of DVD player can handle "data" (ISO) discs with AVI (DivX/XviD) *and* MP4 files native, saving you the conversion time. Might be worth it going forward ...