I just bought my first disc brake bike; a (used) Yuba Mondo for school runs, grocery runs, and family rides. There was no question when researching cargo bikes that I wanted the stopping power of discs.
Up to now I’ve been towing the kids around in a Burley trailer hooked to the back of my CAAD10, with dual pivot tektros. It’s been safe, it’s fine. But there’s nothing wrong with more safety.
I dont don’t know if I’ll ever (voluntarily) replace the CAAD10 as my main road bike, though. So it’s possible I’ll still be riding rim brakes for a long time to come. But I’m aware that the next road bike I buy will more than likely have discs. And it’s possible my kids (they’re 3 now, and are great on their Striders) may never own a rim brake bike.