100mA may work for the majority of headphones, but you might want to increase it a bit to accommodate for insensitive, low impedance headphones such as planar magnetic headphones. 200mA - 400mA should do the trick.
You are definitely NOT going to want to use a resistive divider as Jon86 said, and TLE2426 can only source around 20mA per side. You could use a high-current op-amp to buffer Vin/2 which would become your virtual ground.
Is this device going to be battery operated, or only wall connected? Look at the very respectable O2 amplifier schematic for another possibility (although the power section is kind-of sketchy in my opinion, so consider other options first)