(Opinions my own, naturally.)

I think they're right, really.

Obviously you need to require enough friction that the experiences are comparable (e.g. no letting someone impulse buy 100 times in half a second without having to re-type their "I am an adult" payment info or something analogous, possibly just a hard ceiling for everyone), but I don't think you can ban everything that touches the same sharp edge, and you can't mandate that parents teach their kids how to handle it.

So I think the best you can do is put hard limits on people's ability to hurt themselves without at least an "are you really sure" check, and maybe something like not allowing cash in the exchange without adult verification so the kids might, at worst, gamble their FunBux they earned playing a game and get burned on having lost a lot of FunBux, rather than their or their parents' cash. (This doesn't stop parents from giving their kids their credit card, but that's not really a problem you can solve...)