Brody probably has no idea who the mole is, and Nazir was most likely testing Brody's loyalty by making him take the plans. Sure if Estes is the mole he could have gave them to Nazir himself but maybe Nazir wanted to see if Brody had the balls to do it.
If that was the case, then why would Estes try walk out of the meeting with the reporter while Brody was still going through his stuff. the only reason he didn't walk out was the reporter came up with the idea of dinner.
Unless they don't know that each other are both working for Nazir.