Check out the Lectric Expedition. It is a great value and well-reviewed. Note how the cargo rack is part of the frame. Lectric is the least expensive brand that is considered good quality and has good after-sale customer service.
Transport friends, kids and oversized loads with Lectric's Xpedition electric cargo bike. Featuring pedal assist technology and foldability. Shop today.
lectricebikes.com
They even sell multiple seating options. One of them is a proper seat that can actually carry an adult!
This is a long tail cargo bike, not a small one, but look how versatile it is!
We have one member whose wife and two kids were hit by a car with the Orbitor option and they all survived. I think that says a little about the sturdiness of it. (and also, about their state of karma)
For my part, I don't really NEED a bike like this as my two kids are big enough and would prefer to ride their own bikes, but I WANT one in the worst way! I have visions of mounting the front rack & basket, buying the huge panniers and replacing my car for all local drives for three seasons.
A mid tail bike would be something like the Fiido T1 Pro. It has a tall, integrated rack, but is not as long, and your kid would be right up against your butt:
Fiido T1 Utility Electric Bike
fiido.com