"to the gaily grinning grooms"

I've also given a bit of thought to some other ceremonial aspects.

"who giveth ....?"

Giving the grooms away : perhaps each groom's mother (if still alive) should "give him away" to his partner. It would be a promise by both mothers to refrain from being interfering.

Giving the brides away would seem to me less appropriate, and indeed not very appropriate for straight marriages either. The father of the bride "giving" her to her husband symbolizes transfer of the paternal property rights in the woman to her husband, whose property she now becomes. This comes from the days when a woman, married or not, was regarded as property of father, brother, or husband. Possibly having both mothers of the brides give their daughters to each other would have an appropriate meaning as being a promise not to interfere.

some Jewish ritual

The wedding tent strikes me as a practical item for any wedding. In hot sunny weather it provides shade for the couple and for whoever performs the ceremony. In rainy weather it keeps them dry.

Crushing of the wine glass underfoot symbolizes the breaking of the bride's virginity, and thus it is probably very rarely appropriate today even for straight couples. It seems irrelevant to gay couples, though I suppose each partner could crush a wine glass simultaneously with the other partner doing so. But filling the glasses with wine and inter-twining arms and drinking it might be a more enjoyable ritual. (Grape juice for me please.)

the first dance of the mated couple

For a pair of brides, let me suggest that they waltz to "She's Always a Woman to Me". Re-writing the lyrics to fit the individuals would be an optional variation. So would simply using the music without lyrics.

For a pair of grooms, let me suggest they waltz to "The Man I Love".