God Parents?

My sister has asked my wife and I to be the god parents to the child she is going to have next month. This poses quite a few paradoxes for me. First - it conflicts directly with my stated desire not to have children of my own. It would be rather ironic if I were to then have to raise another person's offspring. The second "sticky wicket" (I am not sure where than came from) is that I don't believe in god, per se.

I told my sister my decision hinges upon her always wearing her seatbelt and stopping smoking ASAP.