This is incredibly shitty of you. Fix it now, please.
At the very least, give Abi and Martin the chance to retrieve their kid’s email archive before you delete it. There’s no excuse—legal or moral—for failing to do that.
I’m not someone who engages in elaborate displays of sarcastic incredulity whenever Google does something less than perfect. It always seemed to me obvious that “don’t be evil” was an aspirational sentiment, not a guarantee of perfection. But this isn’t just failing to live up to one’s ideals. This is evil. Fix it.