Hoping I'm not crazy for bringing a teen and an almost teen on a cruise for 12 days.
I thought the same during our three Europe cruises, especially our Med cruise as we were going to visit many historic sites, and ended up pleasantly surprised. Our teen was far from bored... in fact, he was so intrigued by the Statue of David in Florence that he started admiring sculptures we encountered on the rest of the trip. (We did the Western Med, the first part of your cruise.) Enjoy!