1. You should each create your own named playlist in iTunes
2. When completed, sync your iPod. Click your ipod in the left iTunes menu under devices. In the sync menu bar click music, click Selected Playlists, click the playlist or playlists you have created for your ipod
3. click apply at the bottom right.
4. Do this for each of the ipods
5. Manage your ipod music by using the playlist(s) you have chosen for your ipod
6. All further syncs will automatically use your chosen playlists, and not interfere with the other ipods