After some thought, I think I have found a way to have Equestria and it's solar system be like every other planetary system known, without actually having a Sun and Moon orbiting a habitable world.

The idea is as follows: The Sun and Moon only 'appear' to be being moved by Celestia and Luna. What in actual fact happens is that the Princesses are rotating the PLANET to make it appear that they are raising and lowering the sun and moon.

This can happen, if the moon's location is at the Lagrange point behind Equestria from the Sun. Rotating the planet would look to those on the world to be moving the sun and moon, and not altering the planet's spin.

The magical 'Ley Lines' of the world keep the moon in it's place in the sky, opposite the sun.

In FO:E, Celestia and Luna both die, and there is a terrible disruption of the planetary ley lines, thus freeing the moon from it's long accustomed parking spot behind the planet from the equestrian sun. Thus, ponies in FOE experience eclipses, and times when both sun and moon are in the sky at the same time.

Even though Celestia and Luna are turning the world, instead of moving celestial objects, they are Still far more powerful than any unicorn, or group of unicorns, ever known or assembled.

I know this will prove to be an unpopular theory, but it is one that just had to be stated.

Agree, or Not. Your choice. But I would like something other than 'but that's not canon!' as a refuting argument.