I did this trip October last year and loved it. Recommend you do all the optional trips, particularly the Mount Vesuvius one - it's quite a climb, but well worth it. Last October the weather was a bit cooler than expected, and the day we went to Capri, it poured with rain which meant we couldn't take the chair lift. The weather didn't in any way spoil the trip for me, but hopefully the sun will shine lots for you this October!