Wow what a nice kitchen. I don't think you should do wood because it would look out of place and would match only the beams on the ceiling. The Crate and Barrel Tigg metal chairs look great but its your choice ;D

I think the family members who will be using the stools should sit in them and see how they feel....me personally I hate metal because it takes on the temperature of the room which is generally cool. Also when you are sitting at the counter the quartz/marble/granite will be very cool too, so if it were me I would lean toward comfort and warmth. A good option is woven seats that are warm and soft and comfortable as it upholstery. Sunbrella makes cleanable fabrics in a vast array.....good luck on your gorgeous kitchen....!