Apply for your Active Kids Voucher before you register:
https://www.service.nsw.gov.au/…/apply-active-kids-voucher

Player Fees

$100 or $0 for 1st child (with $100 Active Kids Voucher)
$100 or $0 for 2nd child (with $100 Active Kids Voucher)
$100 or $0 for 3rd child (with $100 Active Kids Voucher)