Whoever's on the KYC, that's the person the casino sees as the one playing. And since we’re talking about a big win here, of course I’d allow my KYC to be used if it’s my own kid. That’s money to enjoy.
There’s nothing wrong with doing KYC as long as the casino is legit and can keep your info safe.
And man, if it’s a big win, no one’s gonna say no to that, right?