If you're a company driver, most companies require children to be a certain age before they can ride along. Werner for example will not allow children to ride if they are under the age of 10. They also will only allow 1 passenger at a time.
If you're an owner operator, it's entirely up to your own discretion. You have to consider the needs of your children, along with their behavior etc. And you need to decide weather or not you can care for a child in that sort of environment.