Elspeth does a fair amount of the negotiating for this - she does run PR. Harley, presently thirteen, is allowed to sit in on a few of the storyboarding discussions - the documentary will not be fictionalized, but they still have concern for narrative flow. It's going to be very long, after all.
Significant portions of the documentary will be conjured recordings of events, from outside or even first-person perspectives, but an entire segment is devoted to personally profiling members and peripheral associates of the Golden Coven, one by one. Harley's not on the list - it's mostly a history documentary, with younger generations present almost entirely for 'where are they now' color, and he's not, technically, her son - but Elspeth and most of her family is. And Harley is permitted to lurk around the studio setup while various people prep with their interviewers, or eavesdrop, or - if they are sufficiently non-vampiric to allow makeup to stick - get that applied. It's a big production; the supernatural community would have found it just as convenient to spread it out, but the film people want everything taken down, edited for a consistent look-and-feel, and released according to schedule within a certain time frame.
So there are a lot of people around. Mostly vampires, but plenty of hybrids - there are most of Emmett and Rosalie's kids, over there, with the proud parents themselves - and wolves; Jacob is over with Elspeth - and even a few humans, ranging from imprints to Lizzie who's with Carlisle, Esme, and Lily, and also Alice and Jasper and their son Brandon. People not normally seen around the Golden Capitols have been hauled in. There's Marcus, no longer as craquelure thanks to magic, and Didyme at his elbow, literally radiating happiness. (Bella rendered her power opt-in along with several other mind-affecting abilities that can't be turned off, but it's very inviting, so people usually do so opt.)
And of course Bella and Edward themselves are present, flitting around, mingling. Their interviews aren't until later.
Kerron waves to Harley when he shows up.
"I was not much of an active participant by the time takeover was attempted," Marcus says dryly. "It was easier to do as Aro and Caius asked than to attempt to gainsay them, and I was much drawn to ease after my mate was killed." He lets go of her hand and puts his arm around her shoulders; she pats the back of his hand. "Aro feared the coordination humans were capable of in the face of vampire fractiousness - it was why he was so pleased to find Chelsea, and to have me to abet her - and Caius desired power."
Bella finishes looking over somebody's clipboard of checklists, and has a moment of stillness, no longer running around micromanaging everything to her satisfaction.
"I don't think that would be pleasant for Kerron. Also, I think he might call off the experiment before it happens."
"All the other witnesses would presumably be too busy mopping up the aftermath to think of notifying me."