I forgot about Dean. Dean was there, of course. I imagine he was catching up with everybody before and after Kingsley had finished speaking and they all had their say related to the plans.
Dean would have volunteered to help Bones, of course. He would also have likely been sitting with Seamus (and Susan).
He would have spoken with anybody who would have spoke to him, and even those who hadn't because Dean is just a friendly guy like that.