Hi shelleyharland
Welcome to the Apple (user-to-user) Community.
Re: When will Apple Cash be available in Australia?
We are all Apple users, like yourself, in this community, so we do not know what Apple intends.
(Also some countries, financial institutions, governments, etc. may not wish to participate in Apple's financial products / possibilities.)
Apple Cash seems to be mainly for sending / receiving money with trusted friends or relatives,
To set up Apple Cash:
Currently, one needs to be at least 18 years old and live in the United States.
US families with younger kids can also participate.
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Re: "kids (10 & 12) and i'd like them to have access to a card/cash"
The youngest that one can use Apple Pay is 13 years old (date of birth in their Apple ID) although kids in some countries do have credit / debit cards available from their financial institutions earlier than that.
Apple Pay requires a debit/ credit card / can be set up on a Watch / and can be used to pay merchants etc. for purchases.
Learn where to use Apple Pay - Apple Support
Teenagers would need a credit / debit card from a supported card issuer:
Apple Pay participating banks and card issuers in Asia-Pacific – Apple Support
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Seems there are various companies (like Spriggy) in Australia, that can issue cards for kids, that can be managed through a parents wallet. (Don't know how reliable these companies are, or whether their products can be used on watches.)
Seems to be a way for parents who don't mind paying a fee, to manage pocket money digitally, until the kids are old enough to have, and manage, their own accounts.
All the best :-)