Let's take this step by step.
This is your statement upon which I am basing my question: "[objectivism is] about doing what makes you happy. And using his powers is what makes him happy"
This is what I'm asking you in response: If The Incredibles is an 'Ayn Rand Story', Why is Dash happy at the end of the film despite being told to use less of his power?
spoiler (click to show/hide)
this is what you've implied in your response to my response: The Incredibles is an Ayn Rand story because Objectivism is about doing what makes you happy, and Dash and the rest of his family are happy using their powers. Dash is
also happy
relinquishing his powers because he likes to do what his parents tell him to do. His parents are happy to tell their son to do less than he is capable of doing because they like keeping their identity a secret. Each of these elements are considered part of any 'Ayn Rand Story'
Is there any part of this that you would like to rethink?