Re: Attendance Kylo was definitely in attendance, because he wanted to meet Q's new friends, but also because Eliot was going. He is a long way from an extrovert and comfortable in these sorts of situations, but he would have talked easily to the people he knows well, Q & Petunia, for instance, and probably been beside Eliot, and likely joined in conversation that he knew enough to say something about.
And he would have been friendly to anyone else who spoke with him. He probably particularly sized up Napoleon because Q told him things, and he knows.