Cement Block & Metal - Wired, Powerline or ?

Hello,

I am helping a local charity extend their building's wireless coverage. The building is a cement block and metal structure approximately 300 feet x 100 feet. It is subdivided into classrooms, offices, kitchen, dining room, etc. with a central hallway running the length of the building.

Currently the ISP drop is in the center of the building connected to a Charter supplied SMC-8014 Modem/Router (4 port). That is connected to a Linksys WRT54GL which provides an additional 3 wired connections and a wireless access point for the central area of the building. So, currently, there are a total of 6 wired connections and wireless access for the cental office area only,

They would like to have wireless acess at each end of the building. The signal is not strong enough with the current arrangement. There are numerous cement walls between the current wireless access point and the ends of the building

There exists 1" metal conduits running from the ISP drop point to each end of the building, originally put in for telephone wiring. These are available for use.

Now the question (at last...   )

What method of extending wireless access to each end if the building would provide the most reliable access keeping in mind that no one in the building is technically adept?

Thus far I have considered:

1) Run CAT5E (CAT6?) UTP through the conduit to each end connected to a wireless access point?

2) Powerline ethernet?

3) More powerful wireless access point inthe center of the building? Maybe an "N" router?

Option 1 and 2 will require and additional switch at the ISP drop to connect the additional lines.
Option 2 will still require addtional hardware which will cost as much as a bulk roll of CAT5E (CAT6?) cable.
Option 3 - With my limited networking experience it looks "iffy". Cement, steel and wireless... hmmm....

Any suggestions/advice would be appreciated. Reliability is the driving consideration here.

Thanks in advance.