Yes, Rat Terriers can be good with kids, but early and proper socialization with kids is key for Rat Terriers, as they can be territorial with their toys around smaller beings. They are typically fearless and energetic, which means they can make wonderful playmates to older kids, but pet parents will need to train them to behave gently with children, and vice-versa.
As with any breed, it is recommended that your child is always supervised when interacting with your Rat Terrier to keep both the child and dog safe.