A lot of couples in Ireland who are not religious and perhaps may not believe in God choose to marry in a catholic church for whatever reason, maybe because its expected of them. Many attend the pre marriage course because they have to in order to marry in their local or chosen church. And many have requested all sorts of things to be left out of the mass. If the priest is ok with it then you can do whatever you like. Although i doubt very much if he will leave out God!