i would deffinately leash. a shrieking child is something a dog simply cannot understand.hopefully time will difuse the child's fear and the child needs to learn not to react this way so that another dog in the future will not bite him because of his fear. The leash might make the child feel you are more in control and will keep the dog safely away where nothing bad can happen. We always had dogs around the kids my mom kept, but they were 100 percent reliable..good ol Scamper knew when she had enuff and could have her own place for peace and quiet, but as long as the child is in your care..his safety has to be your first and foremost concern even above and beyond the dog. A shreiking screaming child can make dogs that have never bit react totally opposite of their nature..especially if they explode in the dog's face.