Danzou was going to take one of the kids no matter if the kid wanted it or not. Kabuto having the most skill of them, have sacrificed himself to be the one that goes (although his mother might not have sensed him, when he was spying on her talk with Daznou), as he had greater chance of surviving than those kids.
And again, read the chapter again. Even when she agreed to work for root to protect the children, Danzou was going to use Shisui's Sharingan regardless of her agreeing or not, to make her a "better" spy/ninja. The only reason he didn't do it immediately is because Kabuto was watching their conversation. He probably made her forget about them or make her emotionless, or something along those lines.
Oro exactly knew what happened, heck it's even possible that Oro was forced to work for Danzou himself (although it feels like this jutsu might be used only once per person, otherwise it's too good. Not to mention that Hashirama's DNA shortens the cooling time).