Why not just keep it simple (stupid ASStronomers)?
How about calling anything a certain size a planet? I have suggested over the years that the size be 2000 km in diameter. If we set a size criteria we avoid any stupid future debates.
Who cares if it circles a star? The question about planets in empty space will eventually have to be addressed, anyway. Size matters, nothing else is really important.
This definition would add the Moon, Io, Europa, Ganymede, Callisto, Titan, Triton and Xena to the list of planets in our solar system. Pluto would retain its staus, but Charon would not meet the size criteria. Sedna and Quaoar would not either.