The centrelink website has a max $ amount that is claimable for CCB. This is the amount you deduct the 94.47% from. It says $3.90 per hour so $3.68433 per child per hour you can claim, up to $195 per week (50 hours) for each child, $184.08 per child. As you would not be paying this amount out (3 kids and only $75 per day for all of them = $375 per week, $125 per child per week) I would guess you would be paying next to nothing. And what you would pay, you would get back 50% in the child care rebate as well.
this is the link to the centrelink/dept human resources where you can calculate your CCB/CCR entitlements, you will just need to know daily charges for the daycare centre and your estimated family income amount. It is very accurate.