My 12 and 10yo are using Greek for Children from Classical Academic Press. We're working through it at about a third the pace is designed for. Postage costs are always an issue for us in Australia, so when I was looking at options I made a spreadsheet of the options I found, trying to get the biggest bang for my buck. The unintended result of that was a program that is very grammar heavy but, apart from memorising a few verses, has no 'living' component - by which I mean opportunities to see/hear/read it in action. (This is in Primer A, which is all that exists the last time I checked. I believe there will be more interaction with the language in future books). So I found some books we could use to practise reading Greek and we do that for a few minutes when we have time.
When we finish primer A, CAP mentioned in an email that we could go on to Athenaze. I have some other options on my Amazon wishlist that I'll look into again when the time comes as well.
One of those is
Polis which is immersion and has all the audio as free download I believe. But I don't know how well it could be used without a competent teacher. But it's intriguing