Capacitor Charging

Just a quick question, because i want to know if its possible. My son asked me if a kind of light harvesting robot could be made. That roams around, finds light, then charges, then runs around again.

The intelligence side is fine for my but i was thinking about how to handle the energy harvesting.

I was thinking if the main bot is running at 5v running two very small motors for movement, light sensor to detect light etc.

for the power though, i was thinking could be provide the power from a capacitor? When we find light, the solar panels feed the capacitor. Am i able to use the capacitor to then power a ATtiny and two small 3v motors? Is there a way to measure the current charge in the capacitor? so if it drops below a certain point, it can sent a signal through a digital / analog pin on the ATtiny so we know we need to charge, and another when it reaches a high point so we know its done?

The motors will be operated using simple transistors to turn them on / off

Energy = $\dfrac{CV^2}{2}$ - plug in 2.7 volts and 3000F and you get 10935 joules.