1) The Declaration of Independence, while a document of monumental importance, is not the law of the land. The Constitution is.
2) On the issue of god and the Constitution:
Where the preamble declares, that coercion is a departure from the plan of the holy author of our religion, an amendment was proposed by inserting "Jesus Christ," so that it would read "A departure from the plan of Jesus Christ, the holy author of our religion;" the insertion was rejected by the great majority, in proof that they meant to comprehend, within the mantle of its protection, the Jew and the Gentile, the Christian and Mohammedan, the Hindoo and Infidel of every denomination.
-Thomas Jefferson, Autobiography, in reference to the Virginia Act for Religious Freedom
3) Remember the audience of the Declaration of Independence. It was intended to be a rallying call to Americans, but it was also going to England which
did have a state religion.
4) There is absolutely nothing in the Constitution suggesting those who don't believe in a creator are exempt from having rights. (There are in other governing documents which is horrible)
5) I know you're trying to spark debate, but imagine the precedent you're setting. "If so and so doesn't believe such and such then some law doesn't apply to them." While I can think of a few exceptions* that's almost never the case especially for rights / protections.
*The only thing that comes close is consciencious objectors not having to fight in wars.