Do I need a document from the american councel?

You need a passport issued by the country he is a citizen of. You need written permission from both parents to authorize travel with the grandmother.

There may be other requirements from the country he is a citizen of and the country he will be traveling to.

Agree, what country are you traveling from, and what country are you traveling to?

From North Carolina to dominican republic

So my answer stands. There shouldn't be anything needed from the DR for just a visit, but I would contact their embassy to make sure

And the letter can just be notorized or do I need to contact a lawyer?

A notarized letter should be sufficient.

I'm wondering why this is a concern? Is there a custody issue here?