My experience last month in Penang International Airport PPL: I have 2 kids, 7 yrs old and 4 yrs old.
1st time, they said 7 yrs old cannot bring in for free, 4 yrs old can bring in for free, I have extra principal cards to let PPL swipe to let the 7 yrs old go in for free.

2nd time, they said both can go in for free, no need to swipe the extra card.

Conclusion: It depends on the staff in charge.

RHB Platinum (4 times free per year per principal), RHB Platinum annual fee can be easily waived by calling CS (My past 2 times experience)
AEON Gold (6 times free per year)

For RHB platinum, normally I don't use it at all. I use it only when RHB have special promotion like Buy 1 Free 1 (friday) during some of the months for secret recipe, kenny roger and so on and also on 30% rebate on certain restaurant during birthday month. That's all. very few transactions per year. When the card anniversary near, I will call CS to cancel the card and they will immediately offer annual fee waiver with conditions - in the next 30 days, swipe 3x and the annual fee is waived. So it is super easy. Worth to keep for the 4 x entry to PPL per year.

Entered into Penang International Airport PPL for International Flight on 8 June 15 using AMEX platinum credit card, wife entered using supp. Found out it doesn't have a shower facility. PPL for domestic flight however have shower facility. Really strange! Food OK.