there.

With only 2 guys hiking it, my guess is that they will be done in 4-6 hours depending on whether they run into anyone on a rappel.

I suggest taking two cars (even with only 2 guys hiking) to leave one where you hike out so that you can drive back up to the trailhead to get the other vehicle.

Rent drysuits. The water will be really cold, and I have never been on Subway when I haven't had to swim at least one time--I have hiked it 5 times.

Have harnesses for each hiker with the right gear for the trip (ropes, fig 8, webbing, etc).

Sounds like a lot of fun!