Something was wrong here. There was a twenty year age gap that should have easily assigned Tony the responsibility to feel this out logically and Kate was the one saying stuff like 'fuel-efficient'. No wonder Tony couldn't get a handle on her. Without context, he abruptly asked, "How old are you?" only to reconsider and wave it away before she could answer, deciding he would rather not know. She might be seventeen and Tony would have to make her stay inside and promise not to talk to any strange men. Besides, it was much more important to explore this 'pretty essential piece' thing, Tony didn't actually hear it very often and he was pretty sure Kate wasn't hitting on him. Wait, back up, "Eighteen, twenty?" It was good to know.
It definitely wasn't up to Kate what and when Tony told his team, she would just have to trust him to make the right call. Like he would about a zombie resistant vehicle, please, he could handle that. What did she think he did all day? Informing the team was just a detail, and he was sure they wouldn't have any qualms. They were safe up here above the horde, they were all incredibly capable, extraordinary people, and they could use a break from each other. It wasn't healthy spending so much time together, the air was already tense enough, they all deserved the space.