My husband and I just did an excursion on Celebrity that took us to Taormina and Mt. Etna. It was absolutely fabulous. We were also only in Messina for 9 hours, so I thought booking the tour would help maximize our sight-seeing time. It was truly phenomenal. The tour took us to see the Greek Theater in Taormina, and we had a little time to do some shopping. Found a 19th century cameo ring in an antique shop. We traveled up Mt. Etna to 6,000 ft and had lunch on the volcano overlooking a series of craters. Then we had time to walk around and down into a crater. Looked like Mars up there. All of our photos were stolen after that, on a train back in Rome. But I can still visualize the beauty. I would do this same excursion in a heartbeat. Bring warm clothes if you do this excursion. We were there in August, and it was warm at sea level and felt like 40 degrees at 6,000 ft above sea level.
Enjoy your cruise!