Now that was something Alastor could see the positives in -- some sort of a return to secrecy. The price to pay for it was too steep in his estimation. But, some semblance of secrecy wouldn't be amiss.
Nodding as Dumbledore continued, he couldn't help correcting, "Four, four of us," because he suspected the older wizard had meant 'three of you' and was already counting himself out. But, they still had six months and a lot could happen in six months that all four of them needed to be taken into consideration that entire time. He did not espouse an immediate opinion on the question of Vance or Marlene, however, as that would need a few moments' thought.
Potter's concern over the idea of charming Grindelwald was only a brief concern, however, as the subject changed to Voldemort and the ultimate objective. At which point, he got his first glimpse of exactly how out of the loop he had been kept on some things. "Shall I presume Horcuxes are one of those pieces of information I'll be briefed on as we go? Or would someone like to clue me in now?"