Check your clearance first. I'm not sure with the 2010 model, but a friend of mine owns an older Sirrus and can't fit fenders with her winter tires (which I think are 700x32, though I'm not 100% certain). 700x35 with knobs may not be very functional.

If the crush is fine and well packed, I would worry less about the tires size and profile, and more about keeping mud and gravel out of your face. Last summer, I did a loaded tour of PEI, spending a couple hundred kms carrying heavy loads on a crushed gravel trail. My 700x32 slicks gave me no problem.

Also, look into flat resistance.