Childermass quirks an eyebrow in response to the other man's response, which could mean that he would've thought better of him and would suggest another idea, and it could mean that he agrees with this decision. It's better to leave Norrell on his toes, guessing which it might be anyway. And regardless, Childermass will be there, for whatever needs done.

He sits back in his chair after a moment. "You are to have dinner with Vrinak," he says at last. "Tonight. I have made the arrangements. He will accept the invitation when you offer it, I have been assured of that." He does not explain himself further. This is what he does. He pulls the strings for the other man behind the scenes. Vrinak supports his ideas. Vrinak is on the Night Council. It only stands to reason that they should get to know one another much better, especially if Norrell truly wants to cement the man's place behind him.