How do I add an offline encyclopedia to an Edubuntu LiveCD?

I am serving in the Peace Corps in a poor Spanish speaking country. I manage several small computer labs. For reasons of limited networking, old computers, and unreliable electricity, I decided that the best solution for teaching computers here is to have the computers boot up to Edubuntu Live CDs. The learning games can't be beat for the price. However, I need to make modifications in the LiveCDs for this to happen, and I'm not sure what is the easiest way to do this. Specifically, the most important changes I need to make is:

1. to remove the install option in boot up.
2. to add an offline encyclopedia.

I figured out that the best offline encyclopedia option is a copy of Wikipedia. Since I need a Spanish language Wikipedia, I'm probably going to go with Evopedia. Although if someone has a better suggestion I'm all ears.

What I'm not certain of is how to add it to the Live CD. Much of this I'm just going to have to figure out for myself, but a few pointers should would help. Do I just add the .deb packages to the "Pool" folder? That seems too easy.

I've been playing with IsoMaster, which is fine for adding whole files, but no so good for editing them. Do I need to do this from a command line?

Or is the best way to build a PC the way I want it and then make an iso image of it? If so, how do I make it bootable?

I know a few things about Linux, but I'm not a guru, so please have sympathy on someone who just wants to do some good in the world.