Next time, mention that to the kids first. That was bad luck; you got the only member of Hydra who's a dedicated pacifist, and Mitani and Poppy both adore him. And they...well, we've made worse sacrifices in games to avoid needless suffering, before your time, but maybe what happened to Lacerta means we need to re-evaluate a little.
For the record, I'd probably have let them try to talk first. Especially in a situation with tense politics, it's better to be clear on what's going to happen first.