If your daughter and son-in-law researched the kind of dog they wanted and needed, why on earth did they get a large breed, high energy PUPPY and then give it full run of the house? It's THEIR job to correctly train the dog and keep it from accidentally (or otherwise) harming the children, anyone else or their belongings, and that requires CONFINING the dog so he learns that he's on the back of the line in pack order and only gets the PRIVILEGE of freely interacting with anyone when he has learned what behavior is acceptable and what is not.
Owning a dog takes a LOT of work and time, and it seems to me that your daughter and son-in-law can't be arsed to do any of it expecting a PUPPY to somehow magically become well-behaved all on its own. He shouldn't be having the full run of the house until he's around 18 months old and NEVER away from physical control around young children.
Luckily the dog is still a puppy when they love everyone and want to be accepted by everyone, but it won't be long before it may start showing aggressive behavior since it's got free run of the home and no discipline or training. There's nothing wrong with the dog - everything you've described is perfectly normal puppy behavior for a puppy that has zero boundaries.
Your daughter and son-in-law desperately need to commit to the time and work it takes to create a well-behaved dog ESPECIALLY because they have young children and the dog they chose is a large breed, high energy animal. If they won't make that commitment the dog needs to go back to the rescue where it will hopefully be given to a family that will. It's not the dog that's the problem.
If they are willing to make the necessary commitment, then the first thing they need to do is get a properly sized crate for the dog and keep him in it so he doesn't have full run of the house until he consistently exhibits desired behavior. When not in the crate he needs to be watched CONSTANTLY and taught what behaviors are acceptable and what are not.
I VERY HIGHLY recommend the Leerburg website concerning everything one wants to know about all kinds of training for dogs. Ed Frawley is one of the best dog trainers in the world, and from what I can tell it's who Milan based his own methods on. Your daughter and son-in-law first need to learn about dog behavior and pack mentality. Ed has many training videos and books available for purchase on his site, however, he also has something like 10,000 pages of free articles and videos.
About Ed...
http://leerburg.com/history.htm
Ed's Philosophy...
http://leerburg.com/philosophy.htm
Training Articles...
http://leerburg.com/training-articles.htm
There is also a Q&A and forum as well as the best products and toys there are that Leerburg personally uses with its own dogs (Ed won't sell anything he wouldn't use himself) at very reasonable prices, excellent customer service, and he uses packing "peanuts" that are edible, digestible and biodegradable for safety and the environment...
https://leerburg.com/flix/player.php/71/Leerburg_Shipping_Peanuts_-_YOU_CAN_EAT_THEM
= new reply since forum marked as read