Thinking of buying a blue heeler, terrier mix and curious about how these dogs would do with...?

I have a blue heeler/terrier mix and he is NOT good with children under 12, he is very loving but rough and has a hard time calming down enough to stay still to be loved back. He never means to hurt them but he cannot grasp the fact that he has to be gentle. I have taught him to "be nice" but this can only happen after he's expended alot of energy outside. Not all of these mixes are that rough, it depends on the size and gender of the dog. My dog is a male and he is 45 lbs and these mixes can be from 15 lbs up to 70. Teddy is now 3 years old and I can see him starting to calm down and have some ablility to control his energy but still needs supervision around teens so I wouldn't reccommend a dog of this mix for a family with small children unless you have the time to devote to exercise and discipline.