You may want to read online reviews of the movie and watch before you take your kiddo or waste the money ... it's not so good.
"Your kids won’t mind any of these problems, but parents may be concerned by some of the messages the film has for them. Mater is dumber than ever, and his behavior throughout the film resembles that of a kid with ADD who’s just had too much sugar. That wouldn’t be a problem if the Cars 2 didn’t spend so much time going out of its way to laud that behavior. It’s easy to imagine parents going home after the film to discover their kid running around the house breaking things while shouting “I’m a tow truck!” Mater has morphed from being a loyal friend, into a self-centered, out of control buffoon. It’s fun, but as a role model for children, I can’t really think of anything worse." -- Josh Tyler Cinemablend.com
the rest of the full review is here
http://www.cinemablend.com/reviews/Cars-2-5324.html
We go to this site for EVERY movie we are considering watching and they also have a feature to help you decide 3D or not ... hope this helps!