"All around people knew who I was anyway, so I figured I was just gonna put up the flag" -American History X
this describes well how i feel about this.

Take them both out to the range and get sense for what he's like - maybe put the fear of God in him a little.
Your daughter is both your best and worst opportunity for him to learn about your firearm practices - make sure she's up to speed on what should be kept confidential.