To thine own self be true. If you don't have to join in saying the Lord's Prayer, then don't...just stand/sit in silence whilst those who want to recite it.
And AA doesn't have a God, or its understanding of God. Each AA member has their own interpretation of what their higher power is. AA doesn't care what yours is, only that you don't think it's your self. There are people of all kinds of faiths in the AA rooms, from believers in a supernatural deity from the bible, to those that believe that there is no supernatural deity whatsoever. All are welcome.