Don't forget diodes across the relays.Missing 0.1uF caps from pins 7, 20, 21 to Gnd.
Protection diodes for relaysTransistors and ICs must be protected from the brief high voltage produced when a relay coil is switched off.The diagram shows how a signal diode (eg 1N4148) is connected 'backwards' across the relay coil to provide this protection.http://www.kpsec.freeuk.com/components/relay.htm
You might want to provide a rechargeable battery. If the tracker follows the sun until sunset it will be in just the wrong position to power the motors at sunrise. With no power it will have to wait until it gets enough energy from the reflected sunrise light to move the array back to the sunrise position.
The linear regulator wastes some of that precious solar energy. A DC-to-DC converter would be more efficient.
1. mind the total current through 328p when all relays on, better use the transistors for switching the relays.2. I would not use the tracking with those optical homing sensors - add simply an RTC and you can calculate the SUN's position with GREAT precision even at night p.