Rode Teravail Galena at 33mm for the whopping 6 miles of gravel, and for entire week. Seriously, if your having a gravel loop, put some miles in it. The Galenas were great for the gravel, though slow and comfortable for the rest of the ride. The rolled over everything.
You could of rode 23s, dropped the pressure, and been ok.
For the clipless pedals, if you can run the MTB SPD pedals with MTB shoes, you might be more comfortable than with road clipless and road shoes. I switch out my road pedals and shoes for MTB pedals and shoes for Ragbrai and it works well.