I just mailed RC about this exact same issue! I am cruising in June next year and my passport expires in October. I'm hoping that it wont be an issue with my Irish passport and the fact that I'm going on a Med Cruise
I am also flying out of Ravenna for a cruise next year. I'll be flying from Ireland to Venice and then will get the train or a bus from Venice to Ravenna. Think it takes 3-4 hours. Hope this helps!