ZiZiL55:
Here is the link for the LEDs. They are embedded to the switches.
12volt/50mA seems to be the max rating for the switch contacts.
The LED is most likely a common LED without current limiting resistor.
If so, then you don't need the whole setup with TIP122 and 12volt supply.
Just connect the LEDs with suitable current limiting resistor straight to the Mega pins.
Test with a 1k CL resistor, and see if they are bright enough.
Leo..