Express the radius of the Sun as a proportion to radius of Earth:
695500/6378 = 109.04...
Now if a baseball would represent Earth, the model for Sun would have to be about 110 times larger than a baseball. A baseball is about 3" in diameter, so the model for Sun would have to be about 330" (or 27 feet) in diameter.
The answer should be no it is not reasonable to use baseball as a model for the Earth because the Sun would need to be about the size of a hot air balloon!
