My question is twofold: How can I open my mother-in-law up to firearms without making her think that I'm a super gun nut and wearing a tin foil had? What's the best way to teach my brother-in-law how to shoot and how to be a responsible shooter (he's a year older than me, but I have a feeling he will be very irresponsible with firearms)?
Don't.
Your responsibility is to take care of you first , so you can be there for the wife, kid, and new arrival.
Guns are fine and dandy, still there is more to life than "just guns".
Be a responsible husband and father, and by doing so , leading by example , anti-gun types are sometimes attracted to Pro Gun folks.
If questions come up, work smarter and not harder - Delegate.
Find a trusted friend of the family to deal with questions, and make the offer to take MIL and BIL to a range, club, anywhere to watch folks shoot, or even rent a range gun to shoot.
This distances you.
Sure "blame" falls on you for stuff you do not do, still by distancing yourself, and not "cramming down" their throats gun stuff is best.
Responsible firearm ownership means-
Is the mom going to have a safe and healthy delivery?
Is the newborn going to healthy and have ten fingers and ten toes?
Is the first born going to feel involved and a part of all this, or ignored and make to feel left out and jealous of all the attention this new brat is getting?
MIL and BIL will be viewing and taking this all in as well.
Do they see a responsible person that is a firearm owner - or a anal retentive self absorbed gun nut, unable to be father and dad?
Just my take.
Doc, will I be able to run 25/25 at trap after the baby is born?
Why of course
Great, because I have never shot trap and would like to learn, and shooting a straight right off would be great while hubby is home being tied up with duct tape in a chair and the kids driving him nuts