So if your Uncle's wife and kids will be travelling to Doha, here are somethings they will be at the airport in Doha for a visa:
1) So their passport must be valid for a minimum of six months.
2) So they must have a confirmed return ticket.
3) So the passenger must have in possession QR 5000 or a valid credit card.
So if you wish to check this out further, you can talk to some travel agent.