Hey BB - welcome to the boards!
Your post reminded me of when I started riding, some 6 years ago. My 2 sons were teens then, older than your 2 girls are now, and I remember them sitting me down to talk about their fears for me. They were referencing the "crazy drivers out there" while you're out biking all over the roads of the Northwest. I hadn't thought about it from the 'family-member's or spectator's perspective, but I remember discussing it with them, explaining that I was not only training to physically complete long rides and improve my skills on the road, but to make sure I learned how to be a safe rider too. None of us, in our cars or on our bikes or walking, have any control over whether someone is a jerkass dangerous driver, but we do have control about our own riding; whether we ride steady, strong and consistent, not weaving or jerking in and out of the lane. Whether we obey the same traffic laws as drivers or if we blow through lights, stop signs and put more than ourselves in danger.
I reassured my sons that I would ride as safely as possible, but if someone hit me with a car, at least they knew I was doing something I loved and that gave me so much pleasure at the time.
May or may not work for you and yours but I thought I'd share...
Mary