7805 Regulated DC Power for two devices
You can use your 7805 regulator to provide a 6V output. How? Take a look at the datasheet:



The way the 7805 works makes it possible to get any voltage between Vin-2V and 5V on the output. The 7805 works in such a way, to ALWAYS achieve 5V between its ADJ and VOUT pins. So the output voltage is as follows:
$$
\frac{5V}{Vout}=\frac{R1}{R1+R2}
$$

Pick R1 and R2 to get 6V on the output. Afterwards, you can use diodes to drop that voltage a bit. A single diode provides a forward frop of approx. 0.7V. Depending on your actual requirements, you might get away with using two diodes and a 1.4V drop. You can get 6V and 4.6V. Depending on your requirements maybe you can get away with 6.2V and 4.8V. You can also try using diodes with different voltage drops to get a better output. 

OR, you can use a separate regulator, since they're so cheap.