That's a very tough question to say you will definitively do one thing or another. If I'm close enough where I can grab the wrist or gun I would attempt to disarm him before trying to draw on him. It's also possible to have control of the wrist/firearm of the assailant and be able to safely draw your firearm if you are on the dead side or on the ground. These are not easy things to do though and takes a lot of training. I've had several weeks dedicated to firearm disarment work in Krav as well as work on it several times a week at home. While I am very efficient even against a fellow student who resist even knowing what I am doing, I understand things change when your adrenaline is pumping and it could mean the difference between life and death for you or a loved one.
The only other way I would draw is if there is enough distance between the assailant is if there is cover or concealment nearby. Create a non complex diversion, while drawing getting to cover at speed. Depending on the situation I may be able to return fire while running. Of course this option is out the door with my family.
For me, very likely if there was more than 5 feet between the assailant, my family and I very likely would have to comply. I'm not a super ninja or anything so I know what my limitations are. If my situational awareness fails my family and I, all of a sudden it is going to take some luck survive regardless of my self defense abilities or decision on how to handle the threat(s).