I agree that managing pups and small children is not easy and probably not for the faint heated, but its definately doable with some common sense rules, the children need to be trained as do the dogs, the dogs need a safe secure timeout zone for 'hectic' times as Hannah said. My 2 are allowed to play and interact with the children (apart fom Evie) for the majority but when they were pups and chasing and biting etc, seperation was introduced. My kids had to meet the breeder before she allowed us to have Belle, they had been around dogs all of their lives but she wanted to see them around her dogs, they passed with flying colours. I find it a little sad that some breeders have a blanket ban on no under 5's as they can develop lovely relationships, my youngest DS is now 5 and he and Monty have a really close relationship, after tea him and Montty cuddle up on the kitchen sofa, I will often find the pair of them fast asleep
My son Tom has suspected ADHD and finds training the dogs very therapeutic he is my chief dog walking companion. Dogs and kids can work but it takes hard work
I have watched the video , the boy is behaving as if he is embarrased which unfortunaterly is giving the wrong signals to the pup.I don't think he is purposely teasing her. My advice would be to forget trying to video the behaviour as this is probably causing more trouble. Get a good behaviourist around when the kids are there so he can see the interaction and give them advice too, good lkuck and try not to worry, looks like normal puppy behaviour to me