Okay, here's my guess: 3 hours 29 minutes.
Here's how I came up with it.
1st leg of (33miles * 1.2) as figure 20% more riding due to zig zag course from side on shore wind = 39.6 miles ridden / (30 mph riding speed * .8 efficiency from riding over waves) = 1.625
2nd leg is similar except 1.3 as zig zagging more due to side shore wind, and a little slower riding going downwind.
So:
Leg 1: (33*1.2)/(30*.80) = 1.625
Leg 2: (25*1.3)/(25*.70) = 1.857
Total 3.482 or 3 hours 29 minutes
Holy crap I spend way too much time in the cube....
Good luck all, sounds like a blast.....