Can MacBooks (10.4) stream music to Bluetooth headphones? If not, is my only other option to purchase bulky/expensive wireless headphones, or is there another way?
Bluetooth audio only works in 64 kbit/s mono quality via the headset profile in 10.4.
Probably not what you want for music listening, even if the headphones support it. As to the second part of your question:
You are stuck with wireless solutions working via the audio jack, USB or FireWire.
In the case of USB / FW solutions (if such wireless solutions exist), check these for 10.4 compatibility before you invest.
Yep, Bluetooth works. Take a look a this :) A bit expensive, but I'm sure there are a lot of alternatives around.