Voldemort didn’t send anyone; Draco was in charge and was the one who brought them there. Voldemort simply stayed hidden, waiting for the news of Dumbledore’s death.

Bellatrix wasn’t present during the event, and Fenrir Greyback came through the cabinet as well — because, really, who was going to stop him?

The exact method of how he communicated with other Death Eaters is never revealed. That’s why a set canon books from another character’s perspective, like Draco’s, would be incredibly valuable.

Tbh I wish Bellatrix was there. Would have added a lot (and yes I know she was there in the films)

I'm gonna headcanon that Draco wrote a letter to Bellatrix.

The exact method of how he communicated with other Death Eaters is never revealed. That’s why a set canon books from another character’s perspective, like Draco’s, would be incredibly valuable.

I'd say the Dark Mark has something to do with it. Perhaps Voldy has a similar connection to his DE's through that as he does through Harry with Harry's forehead scar.

If Draco was the deciding one, why would he not bring his dear aunt?

He also said that he didn't know that greyback would be included, which means that he didn't decide who's coming

If Draco was the deciding one, why would he not bring his dear aunt? He also said that he didn't know that greyback would be included, which means that he didn't decide who's coming

He didn't decide who to come, he decided when to. Who's coming is up to the Death Eaters’ choice, if not what Voldemort set up from the very start.