For comparison, here's how the Earth and the Sun look from the Moon:
So from Charon Pluto looks quite bigger than the Earth from the Moon, and it must be quite a spectacle. The Sun instead looks not much larger than a pin from Pluto. From the Moon it isn't so big either. In fact as it is well known it's about half a degree in angular size, the same angular size as the light disc a few millimeters across in the picture above seen from a few decimeters far.
I personally perceive the the Sun much bigger than this, but it must be just a psychological illusion.