Haven't read everything, so this may well have been said already but here's my take on it -
If you voluntarily elect to have a dog, that dog IS part of your family. It will be every bit as attached to you as a child, in many (not ALL) ways it's like having a child. And likewise, you will, or SHOULD have the same attachment to the dog as it has to you. If you aren't capable of having such a connection with a dog, you should not have one, Having a dog is not compulsory.
I really see no point in having a pet of any kind, much less a social one like a dog, and not really giving a hoot as to how the dog feels about situations.
Your in laws will be aware of why you want to take the dog, because you can communicate with them on that level (provided they're human) - the dog will have no idea why you would leave it behind, won't be aware that you'll return and will likely be miserable. With dog comes much responsibility, people who aren't prepared to shoulder that much responsibility should, quite simply, not have dogs.
With all that in mind, take the dog, if your inlaws don't like it that'll be their problem.
He is your friend, your partner, your defender, your dog. You are his life, his love, his leader. He will be yours, faithful and true, to the last beat of his heart. You owe it to him to be worthy of such devotion.
Sadly, I'm unable to find the original author of the above quote, I saw it on a calendar once. Dog people will understand this, not-dog-people will not. And there's little we can do about that unfortunately.