Let the churches do whatever they want. If gays want to get married they should be able to do so at City Hall. To be fair, I would require all couples to legalize their unions at City Hall, instead of vesting governmental powers onto religious leaders. The religious ceremony would not be legally binding.
Churches can call marriage whatever they want but the government should call it the same thing for gays and straights. Civil union is fine by me.
If we allow gay marriage, we will see more immigration due to that. The marriage and divorce rate will increase overnight. Lawyers, and financial planners should be jumping for joy.