There seems to have been some variation in how much the hosts retain their own will, but once the PF starts to exert itself, it seems to take over. I think Emma definitely needs to be detained until they can look at the scenario, but my guess is in the end, she's not fully culpable, if at all.

As for Luke, I think it's a personal and understandable choice. I have often thought that people who take jobs where they risk their lives on a daily basis should think twice about procreating. I think that ultimately it's personal, but I do think it's one factor to take into consideration.