"Glad I gave you that coffee back when you was watchin' them littluns. Karma in work, right?"

He has to joke, first, just to blunt the edge of strong feelings. That she'd actually done it, she'd kept them safe for him when it would have been so easy to just throw them in the luggage carriage and forget about them.

It's that blunting that keeps his voice more normal when he says, "Thank ya, Darlin'."