Honestly I'm not sure I see the big deal or gamble here that others do, more a relatively well calculated bet with a side benefit of "doing it for a friend". Like, let's be real here: fundamentally the kids are highly sympathetic, and the murderer and their father are not. The stalker didn't "just" kill Ai, but also her frigging doctor. Who was doing reasonably well and was popular, and at any rate few things are less sympathetic in society then killing those who literally devote their lives to helping others. This is also pretty good timing, if Aqua and Ruby had been known as her kids from the start and the whole tragedy it would have made growing up difficult and left them in the shadow, but instead they've "grown up and succeeded all on their own" without even the suggestion of riding on their mother's name and with real tragedy. There's definitely a scandal here, but not one that should really touch them in the slightest. They're still "kids" too.
This does of course alert the father, but Aqua has been hitting dead ends and he's realized there must be other people in the biz who knew or at least guessed about it. This shakes the tree in a very public way while also coming from "an independent source", a journal known for investigating too not just printing rumor. And while some might have wanted to cover up a "lying idol" incident Aqua's former-self murder is a further ace in the hole here to apply pressure to everyone keeping secrets and bring in a whole powerful sector of interests that might not normally care.
So yeah this seems like a very good time to play this card for maximum value. They'll face a storm of media yeah but they're well placed to handle that. They've got friends, connections, real achievements, an agency, experience, and are the victims. It'll be fun to see how they run with it.