Very difficult questions.
As a Christian, I believe that marriage is a committment between two human beings, made to each other AND to God, to become one, forming a family, even if the family never grows further.
However, society, LONG AGO, declared that any two heterosexuals who wanted to live together could call it a marriage. They have civil ceremonies all over the place for it, and a lot of them don't even mention committment to God.
In my head, I DO differentiate. A marriage is a holy union and a vow made to God, a wedding is a civil ceremony blessed by the government, that often goes hand in hand with marriage.
Given that we allow adulterous couples to marry, that we allow people whose only interest in one another is lust - to marry, that we don't care if people have never been married before or if they have married and divorced 15 times before - -- it is hard to say that what the government condones as marriage has anything to do with God beyond the fact that Christians still make vows to God while going through the civil ceremony.
Given that - what Homosexuals want is the same thing that other non-Christians who marry have. They want social security benefits from someone they share their life with, they want tax deductions and insurance and all the things society says goes with marriage.
Personally, I'm in favor of saying, "If it isn't a religious thing, don't call it a marriage at all, call it a family-contract," and let ANYONE who is marrying for reasons other than religious reasons participate in THAT, and leave marriage to God.
I don't think homosexuality is God's will, but I don't think it is any less God's will than a lot of heterosexual marriages that we bless are.
I want marriage to be an ordance of God's church, and I want the government to get out of it.
Let the IRS deductions and insurances and sick-leave designations be whoever a person says, "I consider this to be my immediate family," but don't call it a marriage.