I'd go for keeping Bonnie's room "a place of mystery" for now. Let the other cats' curiosity get the better of them. Keep the door partially open to a crack and let the sniffing begin. Sooner or later one of them will feel brave enough to encounter "what lies beyond" and can report back to the other two.
With us, it was Moray facing an invasion of velociraptors. And Gurls at that.
He was the one outnumbered, and - laid back gent though he be - he was a bit hissy and withdrawn initially. We kept the girls in the room on their own a bit longer - they got to explore after about two weeks, moving them room by room as they got a bit braver (they were terrified when we initially brought them home, as they'd got off to a very poor start in their very young lives, so they needed longer to adjust).
Don't rush introductions, however tempted you might feel. Let the older existing cats set the pace. Kittens will just want to play, so Bonnie will have no qualms about encroaching on territory, head wrestling and other obnoxious and perfectly normal kitten behavior. It's your older cats that need the time to adjust to this new interloper and ball of fizz.
She's a little peach, isn't she?