i am flying for the first time with my 3 year old what documents do i need to board the plane with my family besides boarding passes?

You need a birth certificate and Social security card

TSA website provides what you need for security and what you can carry through versus bag-check

For your 3 year old I would bring the birth certificate as proof of age if you got a discount. And also that should be enough verification for the airline to verify that it's your child.

Drivers license. If you go on to the website, you should find information on what you need.