It was a bit tricky to decide how historically correct I should try to be concerning the Mycenaean religion. As I've mentioned before, some of the gods and goddesses of the classical period can be traced back to the Mycenaeans, but the only thing we have are their names (or names that are similar to their names) on clay tablets. It is not possible to tell whether these deities had the characteristics and responsibilities attributed to them later.
For instance, I've read that Zeus was a member of the Mycenaean pantheon, but that he was by no means the chief god. Poseidon seems to have been a more important god than Zeus was, at least if you look at the scale of offerings registered at the remaining tablets.
My idea was that Zeus and his siblings are more or less established as gods when this story takes place and that Zeus already is revered the most, but that the importance of the Great Goddess still is lingering since the Minoan period.