I wish Kyouko and Haru had been able to get more involved earlier, but it's true that they don't have experience in fighting unlike most of the gang.
Wow, Lambo's weapon is wicked!
I'm glad the girls spoke up, everything they said is right. They deserve to know. They're already in danger, they may as well know as much as possible and be equipped to deal with it if get in even more danger.
If it were me stuck in the kitchen doing chores the whole time while all my friends were off getting stuff done and hiding everything from me, I would get tired of it really fast. It's better to at least be told the basics if you expect them to be docile.