A tourist visa would be no issue at all. My family come over on tourist visas to see their kids, their loved ones and no one gets denied. It’s just a holiday to visit family, he might get asked what the purpose of his visit is on landing but the answer is visiting family. Totally normal.
Does he just not book a holiday like everyone else? And sort out the admin/visa for the period of time he is staying?
He'd likely need a flight back already booked and I don't see why a normal tourism visa wouldn't work. He's only visiting!