For hiking/biking/walking: Appropriate sportswear, cycling wear, hiking shoes, sneakers, light jacket, etc. Inquire about cycling - most operators provide helmets, water bottles, etc. For cooking classes: Classes are casual (jeans, pants, shorts, comfortable shirts - avoid long sleeves) For excursions: In case you end up in a nice restaurant at the end of the day, you might want to dress up a bit more than casual (no jeans or shorts).
I have found that in Tuscany, Provence and the smaller villages of Portugal and Spain, casual dress is widely accepted. I would suggest casual slacks, skirts, comfortable dresses, capris, and "nice" jeans; as opposed to shorts, Levis and dressy slacks. People tend to really dress up in Rome, Madrid, Paris and the bigger cities.