You could, if you wanted, create a few extra folders for backups of those files, too, if you wrote them to a DVD-+R. While it probably never would happen, if you got a bad sector on the disc and couldn't read the files from the disc, the backup folders may still be readable and thus recoverable. While what would most likely happen is a bad sector would either not be limited to 1 or it would, most likely, render the entire disc unreadable, it is a cushion you might fall back on.
You can play those MP4 files directly from the disc you make on a PC. Your DVD/Blu-Ray player has to support playing MP4 to play them from the disc and its navigation has to be programmed to accept MP4 input from optical disc. But, if it does, you shouldn't have problems playing the MP4's back from a disc.