Mining wont do anything to the orbit of the moon. We've been mining the earth for thousands of years and havent effected the orbit of the planet one bit. It will be no different for the moon. To effect the moon's orbit we'd have to remove a massive chunk. Planet cracking type mining and that sort of mining is purely in the realm of scifi and well beyond out capability. Within our lifetimes we might be able to mine helium 3 and do some standard ore mining. Nothing that can harm the moon or our planet.