FelixFelicis:
I would probably use 7805 for the arduino, what about the rest? Is it advisable to use a single 6v supply to all these components? Or should I use 2 separate power supplies?
A 7805 requires higher then 6vdc to meet it's minimum drop out voltage spec for the regulator chip. You would have to use a low drop out regulator, or as I already stated just use a series diode like a 1N4001.
Lefty