I would only take 1 pr of jeans. I did VI last year at the end of Sept and like Terri, the only time I wore jeans was in Lake Orta at the end when it was rainy and cool. I would probably not take 2 skirts but I don't wear skirts any way. Were you thinking dressing for dinner? If so I would just go with 1 skirt as you will probably not really dress up on the group dinner nights. If you are taking the short skirt to be cooler then I would take either the shorts or the short skirt. There were some days when we did not do a church and the shorts/short skirt would be appropriate then, otherwise on the Siena and Asissi days you will need your knees covered, maybe the day in Padova.
Bottom line, lol, is I would take the 2 capris, 1 pr jeans (wear on plane??), 1 pr shorts or short skirt, perhaps 1 long skirt. Well, really for myself I would just do 2 capris and 1 pr jeans (if they are lightweight enough to dry overnight). I only took 1 pr capris and regretted it. I wore them A LOT!!! I would not take skirts or shorts but I don't really wear them at home anyway.
This is such a fun tour! Lots of hands on stuff and demos.