I have seen the ice cap fans in person and they run silently. If you use PC
fans you need to have an AC
converter and drop the voltage from 110VAC to 12VDC. An old computer powersupply will work for this. If you get a new ATX style power supply you will have to hotwire an on/off switch as the new powersupplys require the motherboard to tell it to turn on/off.
I think radioshack has AC
fans for sale that you can wire up to your plugs. Then when the ballast has power the fans have power.
When mounting your bulbs try to use some spacers to keep a small air cavity between the reflector and the wood. This will help keep the wood from getting to hot. My wooden canopy is warm to the touch after th elights have been on all day even with a 1/2" air gap.