I'm all for the slap on the car. It sure makes an impact... Only, the ******** nitwits might not even know why you're angry at them. Half the time I save my own ass and they never notice how close they were to flattening me.
The presence of the toddler doesn't change anything imho. If you think it's ok to yell at her, then do so regardless of her company. At least she may be a bit more ashamed.