Child Guardianship upon parents death

[TravelingMan]

What is the name of your state? New Jersey

I posted this in another section, it was suggested that this would be a better place to post this question.

My wife and I currently have only one child, he is one years old, and we should have taken care of this issue much sooner.

We have both agreed that if we both are deceased and our child is still a minor, we would like my sister and her husband to take guardianship of our child and and his well being.

I hate to bring money into a situation when the future of our son is involved (makes me feel like a crappy parent) but my wife and I currently do not have the resources to hire a lawyer to do this. My question is can my wife and I do this on our own with some sort of standard document to make it legal?

The situation is:
My parents- My wife and I have a great relationship with my parents. In fact they baby sit him during the week when my wife and I work.
They are good people and would follow our wishes. If we want guardianship to go to my sister they would not contest it.

My wifes parents- My wife and I (and my wifes Brother and sister-in-law) have not been on speaking terms with them in a few years. This is because of their erratic, destructive, and mental abusive behavior and actions. They have never been a part of our sons life, and my wife and I agree they never should.

My wifes Brother (and only sibling)-Both he and his wife are good people, they are approaching 50 and never had children. They are a part of our sons life and would continue to be so. I also don't think they would contest any guardianship with my sister.