Synching two ipod with iTunes in Mac-Mini

[Abdulhaq]

I have all my music in my mac-mini. My fourth generation ipod is synched with itunes and I always copy new music and synch this ipod to transfer the newly copied music. I also have a fifth generation ipod which may have slightly different contents than in my 4th generation ipod. I want to copy all the contents of my mac-mini to this ipod also. I am afraid while synching it might delete some songs from my itunes library. Is there a one way process so that itunes will not synch but copy contents to the new ipod? My mac-mini is constantly backed up to airport extreme disk periodically. If I lose my contents then can I enter time machine and restore from the previous backup? I would not mind if both the ipods have the same contents so that I can effortlessly synch either of them with my mac-mini.