We're in a, generally, warm climate. I always dress my children in layers. Even when it's 70 degrees, that is still cool. It may warm up later, of course, thus the layers. We don't have any 'woolens' other than scarves I've knit. Just cotton layers. No logos, I do do a lot of stripes but that is mostly born out of what's available to me and that solids show Soup Day stains more.
One thing that really sticks out in my mind is the layers. I read something once that pointed out if their little bodies are expending extra energy to keep warm, then it is energy diverted from growing and developing or learning. So, even when it's 70 Dc wear two layers until I notice they're hot. Ds is old enough to speak on his own about how he feels so I don't worry about him at school. Now, when it's 80 or 90 or more we just dress in one layer, cottons of course.
I wonder how bamboo fairs as far as breathability? Or Hemp?