A few (possibly pedantic) points. Whatever you book from ANU won't be a connection, it'll be a completely separate flight on which you'll have no protection if your VS flight is late or cancelled. So the usual rules about leaving a lot of time between flights on separate itineraries apply, if you don't fancy buying new tickets. This is particularly relevant for the return flight from ANU. Partly because of this, I would not worry about these regional flights until shortly before your trip, say in September.

I am curious, however. If you booked a holiday with Virgin Holidays in Grenada, are the flights only to ANU but the hotel in Grenada?