The American founding fathers were very divided on many things. Some of the founding fathers such as Alexander Hamilton wanted this nation to become a Kingdom while others like Thomas Jefferson wanted the United States to become a Republic. Religion was no exception. While there was secular founding fathers like Thomas Paine, I think it is fair to say that a majority of them were followers of some form of Christianity. If by secular you mean separation of church and state then yes they intended it to be a secular nation. If you mean secular as in secular culturally then I would assume many of them would oppose it.