I think it depends on how large the mini-excavator actually is. But, I think your project very feasible. Like Chris says, you just need a way to move the dirt once you dig it out of the ground.
I have friend who has done a lot of work at my place with a Kubota compact excavator. It has about a 20-foot digging radius, and can dig about 12 feet down. It is amazing how fast he can dig with that thing. He also has a reasonably large skid steer and a dump truck. Between the three pieces of equipment, he and his dad can move an incredible amount of dirt in a day.
