First take: The government should not be in the marriage business at any level.
Second take: Your marriage has been dying from the moment you became a party of it.
Agreed, pretty sure marriage is a religious thing. Question though, are civil unions given the same tax advantages that marriages are given?
The question isn't whether they get the same tax advantages. Civil unions are not the same as marriage by a long shot in many fashions.
The question is do homosexuals have a constitutional right to participate in marriage? At least that would be the question posed if it reached the level of the Supreme Court. Until then it is "what do the majority voters want to allow homosexuals to do with regards to marriage." The Court hasn't tried a case yet that deals with the above issue, they have either lacked standing or dealt with similar but non-equal subjects (Lawrence v. Texas).
The question would come down to whether or not marriage is an inherent right set forth in the equal protection clause.