תרגום - לטינית-אנגלית - Io Cybele! Io Magna Mater! Impleat lapibus illis...

"io" should be rather "hey", or ¨"Ô" than "hurray", but maybe have you got other sources that let you translate this way?
I saw you didn't translate litteraly "Mulieribus pars vim tua det!"(part of your power was given by women) (but I'm not sure either...) Googling the text leads to an interesting link about this "Great Mother cult", it is told that St Peter's cathedral in the Vatican was built on the fundations of an ancient temple devoted to "Great Mother" cult.
HERE

There are very interestng parallels between Mithras and Jesus, the Great Mother and Mary which seem to have been utilized by the early nazarine sect of Judaism in order to break the paganism of the Roman Empire and in that way take revenge on the Empire for its destruction of the Temple. It may well be that the incorporation of the two main sects in the Roman Empire into what became Christianity was ultimately the very thing that destroyed the Empire and, in later years, came back to haunt the Jewish people.

I'm using the Cambridge medieval to early Latin extended dictionary, 2002. They suggest clearly "Hurray", I reacted upon it too. I thought 'Oh', 'Hoe', 'Hey' and even 'Horay' first, but changed it. but I'll change it back to 'Oh* as I feel that it is more "culty".

The reason why I didn't chose the plural, women, is that they dedication is pointing towards The Great Mother, and (if she isn't talked about in "pluralis majestic" she is 'The Woman' that grants the servants the force (Cult).
Do you think it is better to make a diminutive phrase?

How about behold or hail instead of Oh or Hey?

'Io' is a clear interjection like 'Oh','Hey' etc.

'Hail' is a good suggestion but sounds more strange in the last expression.
I think 'behold' would be very suitable as 2nd interj in the last expression: "Oh, Behold...

I'll try a mixture of all three of them and see what you think!