As long as the USB bus has enough power on it, and it will have if all the USB hubs are powered by external power adapter, then you can charge these devices without a problem.
They do not need to be directly connected to a computer, just to a USB bus with sufficient power.
On the subject of reformatting:
Turning off Automatic syncing on connection would ensure that the iPods would only charge when you connect them and not sync.
Instead of reformatting them, consider having a "playlist" for them, assuming that all will have the same information on them) and when a device is turned back in you simply run the Sync operation which would be pointed at this playlist. The sync process would remove everything that is on the iPod that is NOT in the playlist.
(Sometimes the source of much frustration when the device is given as a present AND it has been preloaded with music by the giver on the givers computer. At first connection to another computer, the auto sync function will sync with new iTunes library and remove all the preloaded tracks! )
Hope that helps