Because of obvious constraints, this ceremony must be short and somewhat
scheduled around the constraints of the ride.

[All participants seated, belted in.  Train ready to go.
 Train starts.]

OFFICIANT

[Yelling]

Dearly beloved, we are seated here today to witness the marriage of
two people, Jennifer Mitchell and Timothy Showalter, in this 
inappropriate but yet legally binding ceremony.

Do you pledge to each other the bonds of matrimony, through

the loops,
the flat turns,
the rainy days,
the positive G's,
the corkscrews,
the double dips,
the breakdowns,
and the screaming?

BRIDE AND GROOM

We do.  [Ideally, we say this just as we're going down the first hill.]

[No ceremony for two hills.]

OFFICIANT

Do you, Jennifer, swear to love, honor, and cherish Timothy?

BRIDE

I do.

OFFICIANT

And do you, Timothy, swear to love, honor, and cherish Jennifer?

GROOM

I do.

[Pause until last straightaway, but before the station.]

OFFICIANT

And now, by the power vested in me by the State of California,
the (whatever) Church(es), and the force of gravity, ...

[train stops in station.]

... I now pronounce you husband and wife.  Kiss!

[Ring exchange will take place after the ride, due to the obvious bad
 interactions between expensive loose objects and a roller coaster.]