Karvan sees the kids and then smiles, actually seeming happy as he moves over, dropping to one knee so he's more on their level and growls out, "Come here, come here you two." He motions to the boy, his face suddenly an animated frown, "First thing, when you fight someone you must remain calm. Don't go all throwing people off of you and then diving on them. That's a good way to land on a dagger." He pats his stomach once to effect, "Also, while biting her on the ear was effective in angering her, it did nothing to disable your opponent therefor gave you no advantage in the fight." He ruffles the little girl's hair and grumbles, "She's a tough one, hurting her in a manner that does not further your advantage in a fight will just anger her, which is not a bad idea if you know how to counter it. If you bit her with the thought of turning her response attack on her in a counter, then it would be proper strategy. You just bit her to cause pain because you had lost your temper. There is no need for that. When you fight someone you need to realize the only pain needed is the pain needed to disable, disarm or kill. NOT THAT I WANT YOU KIDS KILLING EACH OTHER. But if someone is trying to kill you... you... you kill them right back you here me?"
He stands and disarms himself, dropping all his weapons on a table as he drinks a large drink from a mug of ale before walking back over to where the kids are and falling into a fighting stance, he growls, "The problem with a fight is very simple, everyone has a plan until you've got a dagger in your shoulder. Pain clouds the mind, just like anger. You must never be angry in a fight. I act angry, growl, roar even but I am always calm despite my pretending to be other wise. You confuse your opponent, you give a loud roar," After he says the words he lets out an ear shattering roar and snarls, releasing a show mock rage and spittle into the air. Then he immediately returns from looking angry to looking happy and smirking,"If you can pretend to be angry your opponent will think you less apt to counter them and you must fight defensively, if you and your opponent are of equal stamina you can out defend them. Moving your hands the slight bit to turn a punch or, with a shield, parry a blow is a lot less tiring than swinging your full body into a blow." He does a few mock swings and mock parries to show the difference.
Then he pulls the little boy over and growls, "When you want to disable someone you strike them in one of three places. The joints." He taps the boy on his knee, elbow and wrist. "You can strike or twist these areas and the person will be in immense pain. You can't readily hit the elbow or wrist due to a person moving but if you are grappling and someone is putting their hands in and around your face you can get a good grip. The second place to strike is the soft parts of the body." He pats the boy's throat, lower back, and belly. "A blow here is not always instant pain, but it will build up, you hit someone in the kidneys enough and they will go down, no matter who they are and the final place, as shown by our little champion here." He ruffles the girl's hair again, "Is the sensory organs, your nose and eyes have so many nerves in them, getting hit in the nose or a thumb in the eye feels like swallowing fire, but something a lot of people don't realize is that an open palmed slap to the ears can also disorient and disable your enemy. Makes you see double if you do it right."
He smiles broadly, again, after he gives the quick lesson and then stands up. Yawning loudly as he says, "That ale is delicious." He goes back and takes another mug and one of the fresh pieces of produce and munches on it. Then he seems to get an idea and he turns to one of the adults. "Any of you want to spar with me? Give the kids a bit of a better lesson." He looks worriedly at the kids, "I'd hate for anything to happen to them, for them to be unprepared... first time I had to kill a man I was barely more than a whelpling, 13 years old..." He lets out a long sigh and shakes his head a bit, "Sorry, you know, the only opponent I've never been able to kill is my past."
(Dragonborn mature slower than humans I read, but I don't know how much slower. How old an adult dragonborn is)