I believe in traditional marriage and I will answer "Yes"
These days many gay people are living more and more in family arrangements like straight people. In many cases they are raising children. So it is only proper that gay couples wishing to get married should be allowed to do so, rather than be forced to "live in sin". I believe that it is also better for the children if their parents's relationship is properly recognised.
While I believe in allowing people to make their own choices, I think it is advantageous if the way society is structured subtly influences people to live in stable relationships rather than lead a promiscuous lifestyle.
For these reasons I believe that gay couples and also couples with one or more genderless people in them should be allowed to get married.
I am convinced that marriage without gender restriction will come sooner or later. The question is when and on what terms. If you are concerned that your church may be forced to conduct gay weddings, then think carefully about what sort of government you would prefer to introduce gender-unrestricted marriage. While I am not saying that conservative governments are always better, I do think that the nature of the Turnbull government and the Coalition caucus is such that they are more likely than a future Labor government to put adequate safeguards in place.
Consider the consequences if we say "No" now and a future Labor government comes in on a platform of gender-unrestricted marriage, and after weathering a "Put Labor Last" campaign funded and organised by religious organisations. Do you think then would be a good time to negotiate concessions and safeguards? I think not.
A reasonable compromise would be to explicitly legislate such that discrimination in providing services and venues is allowed if all of the following apply:
Such an arrangement would cause little if any practical problems. I think couples getting married would in any case prefer to have services provided by supportive providers.