HowTo: manage updates to Ubuntu offline, via memory key or CD/DVD?

[Leo Mauler]

I'm about to set up two Linux PCs for the Alcott Arts Center (www.alcottartscenter.org) in KCK.  One Linux PC will be running Edubuntu, and most of Project Gutenberg, for their library; another one will have regular Ubuntu or Kubuntu to be run in their office.

These folks are so financially-strapped that the Center doesn't even have a phone turned on (the wires are there but the phone connection isn't active), let alone a broadband Internet connection.  The "Alcott Arts Center" phone is actually a second line in the caretaker's house a block away.  I've already booted up the laptop and determined there are no nearby WiFi hotspots.

I'll run the updates before I pack up the PCs, but after I install them on-site there is no on-site method of downloading updates.  Is there a way to give an Ubuntu update repository a list of installed software on another computer, and thus download updates for another system to be transferred to that system via memory key or even CD/DVD?  I'll continue to have personal access to both PCs for maintenance.