Oh, he knew accepting this dinner invitation was a good idea.

"It is always good to know where potential pitfalls are located."

And it wouldn't do to have the wrong people get wind of this. Not at such an early stage, especially.

"It is always good to reconnect with my old students. I remember Longbottom, well. And I should extend my congratulations to Miss Plume on her new job."

Dumbledore knows Moody well enough by reputation to think he'll not need a great deal of persuading.