Last spring I non-reved on IB and was dressed "Business Casual". I had on cotton dress shirt and khakis, my shoes had a good shine. My kids were dressed a little more casually, but not shorts/t-shirt, either. Also, they weighed our carry on. I don't remember the max, but they will make you check it if it over weight even it passes the size requirements.

Good luck on the Camino. Remember to get your "pilgrim's passport" before you set out. Please post pics when you get back.