I don't know about child support stuff, but I do know for 100% sure that if you opt to claim PPL, this does NOT affect your Parenting Payment Single - Govt Paid Parental Leave is not considered to be income for social security payments. It IS included as income for the purposes of FTBA (i.e. your income estimate) but if you receive Parenting Payment Single you are generally entitled to the max rate of FTBA. For the period you receive PPL, you are not eligible for FTBB, but I think the online estimator takes that into account.

Baby Bonus also doesn't effect your entitlement to other payments (other than PPL - you can only receive one or the other).

HTH!