You are tap dancing. Where are the Founder quotes that they were afraid of Christian participation in government? A bunch of guys opened a meeting with prayer every day, and no correspondence or debate exists that documents their wish to separate their own religious practice from the document they were building?
The state constitutions of Georgia, Maryland, Pennsylvania, South Carolina, Vermont and (most notably) Virginia predating the Constitutional convention all have preambles that reference the Almighty. Are you saying that delegates from those states came to the convention and the subject of doing or not doing the same thing in the federal document never came up?
You do know whey there is a first ammendment to the Consitution dont you? It wasnt out of the kindnest of their hearts. They feared having any one religious group take over the state and force their beliefs on the others as had occured in England and the rest of Europe.
"The clergy, by getting themselves established by law and ingrafted into the machine of government, have been a very formidable engine against the civil and religious rights of man."
-Thomas Jefferson, 1800
"The United States of America have exhibited, perhaps, the first example of governments erected on the simple principles of nature; and if men are now sufficiently enlightened to disabuse themselves of artifice, imposture, hypocrisy, and superstition, they will consider this event as an era in their history."
-John Adams, 1788
Now I have provided you two examples of our Founders eschewing any form of religious government, and even warning of the dangers of mixing religion and politics. It is now up to you to complete your own education.