Be extremely careful who you choose. Family members can be good, but not always. People from your church, but not everyone. People with a military background (ask them to prove it with their DD214 discharge papers). Any combination of the above. These are people with whom you may be trusting your life and the lives of your spouse and kids. OPSEC means Operational Security, which means you only discuss operational matters with those who have a need to know.
Also, as a group, chose a single caliber for handguns and/or rifles. That way everybody has a common ammunition – 9mm or .45 ACP (not both) for their handguns and 5.56mm or 7.62mm (not both) for their rifles.
I swear that I will defend the Constitution against all enemies - foreign and domestic. Sargemsb